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COVID

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the COVID-19 article more useful, or one of our other health articles.

On 31 December 2019, the World Health Organization (WHO) was informed of a cluster of cases of respiratory illnesses, including pneumonia, of unknown cause in Wuhan City, Hubei Province, China. On 11 March 2020, the WHO announced a COVID-19 global pandemic due to the rapid spread and severity of cases worldwide. SARS-CoV-2 is felt to be zoonotic in origin, but the source of the original outbreak has not been identified.1

The original virus strain has mutated over time causing new variants with differing abilities to spread and cause severe disease.

Continue reading below

What is COVID?1

Coronavirus disease is an infectious disease caused by a novel betacoronavirus (an RNA virus) known as severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). The disease associated with it is now referred to as 'COVID-19'.

The National Institute for Health and Care Excellence (NICE) provides the following definitions:2

  • Acute COVID-19 is defined as signs and symptoms of infection consistent with COVID-19 for up to 4 weeks.

  • Ongoing symptomatic COVID-19 is defined as signs and symptoms of COVID-19 infection from 4 weeks up to 12 weeks.

  • Post-COVID-19 syndrome is defined as signs and symptoms that develop during or after an infection consistent with COVID-19, continue for more than 12 weeks, and are not explained by an alternative diagnosis. It usually presents with clusters of symptoms which may overlap, fluctuate, and change over time, and affect any body system.

  • Longer term effects of COVID-19 or 'long COVID' defines signs and symptoms that develop during or after an infection consistent with COVID-19, continue for more than 4 weeks, and are not explained by an alternative diagnosis. It includes both 'ongoing symptomatic COVID-19' and 'post-COVID-19 syndrome'. See also the separate article on Long COVID for further information.

Variants of concern continue to be identified. The UK Health Security Agency (HSA) publication Investigation of SARS-CoV-2 variants: technical briefings provides additional information on novel SARS-CoV-2 variants.3

How common is COVID?1

The global number of people with COVID-19 (confirmed or suspected) is changing rapidly.

  • The UK Health Security Agency (HSA) publishes a UK summary of coronavirus cases and an interactive map, which is updated on weekdays.4

  • The World Health Organization (WHO) publishes daily COVID-19 dashboard maps which provide global (including UK) interactive data on new cases, cumulative cases, deaths, and vaccination rates.5

The UK Office for National Statistics (ONS) publishes regular Coronavirus (COVID-19) infection survey results, which include the percentage of people testing positive for COVID-19 in private residential households with regional and age breakdowns. It also publishes a statistical bulletin of the estimated prevalence of self-reported long COVID symptoms.6

COVID risk factors

Risk factors associated with an increased risk of severe infection and/or death include:

  • Increasing age.

  • Male sex.

  • Obesity.

  • Pregnancy.

  • Other medical conditions, such as diabetes, hypertension, severe asthma, and chronic obstructive pulmonary disease.

  • Health and social care workers.

  • Lower socioeconomic status.

  • Black, Asian, and minority ethnic (BAME) origin.

Clinical subgroups at highest risk of severe infection and/or death from COVID-19 infection include:

  • Down's syndrome or other chromosomal disorders known to affect immune competence.

  • Certain types of solid cancer, and/or received or receiving treatment for certain types of cancer.

  • Haematological diseases (eg, leukaemia, lymphoma, myeloma, myelodysplastic syndrome, myelofibrosis, sickle cell disease) and stem cell transplant recipients.

  • Renal disease (including renal transplant recipients, non-transplant renal patients who are immunosuppressed, chronic kidney disease stage 4 or 5).

  • Liver disease (some forms of cirrhosis especially decompensated liver disease, liver transplant recipients, liver disease on immunosuppressive therapy).

  • Other solid organ transplant recipients.

  • Immune-mediated inflammatory disorders (including people taking some forms of immunotherapy, biologics, JAK-inhibitors, corticosteroids, uncontrolled or clinically active disease, major organ involvement).

  • Weakened immune system (eg, common variable immune deficiency, severe combined immunodeficiency).

  • HIV or AIDS (if immunosuppressed, have uncontrolled or untreated HIV, or acute presentation of AIDS-defining diagnosis).

  • Neurological and neurodisability conditions (multiple sclerosis, motor neurone disease, myasthenia gravis, or Huntington's disease).

Continue reading below

How long does COVID last?

COVID is a very variable illness and it is currently not known how long it lasts. The duration of symptoms and the prognosis are very variable and there is still a great deal more to learn about the illness.

COVID symptoms1

The incubation period for SARS-CoV-2 varies depending on the circulating variant, and is about 3 days for the Omicron variant.

COVID-19 infection can cause a spectrum of illness varying from asymptomatic infection, to mild upper respiratory tract infection (URTI), to severe pneumonia and other complications.

About one-third of people with COVID-19 are asymptomatic. The symptoms of COVID may include:

  • A high temperature, fever, or chills.

  • A new, continuous cough (frequent cough for more than an hour, or 3 or more coughing episodes in 24 hours).

  • A loss or change to sense of smell or taste.

  • Shortness of breath.

  • Feeling tired or exhausted; muscle aches and pains.

  • Headache (that is unusual or longer lasting than usual).

  • Sore throat.

  • Blocked or runny nose.

  • Loss of appetite.

  • Diarrhoea.

  • Nausea and/or vomiting.

COVID-19 infection in children and young people under the age of 18 years is usually mild and a short-lived illness. Older and/or immunocompromised people may present with atypical symptoms, such as delirium and reduced mobility.

How long do COVID symptoms last?

For many people the symptoms last between a few days and several weeks. For most people symptoms resolve by 12 weeks.

However this is very variable. About one third of patient's don't develop any symptoms and symptoms may last long after 12 weeks (long COVID).

Complications

Possible complications of COVID-19 infection vary depending on the variant, the person's age, comorbidities, and risk of immunosuppression, and may include:

Continue reading below

How contagious is COVID?1

COVID-19 virus spreads from an infected person's mouth or nose by droplets from sneezing, coughing, speaking, singing, or breathing. The risk of transmission is highest if a person is in close proximity to an infected person (especially within 2 metres) and/or in a poorly ventilated indoor space.

Indirect transmission may occur due to contact with surfaces contaminated with the virus (fomite transmission).

Perinatal transmission has been documented, however, the exact mode of transmission is not known.

How long is COVID contagious?

It is not known exactly how long COVID-19 is infectious. One study by Imperial College, London found that less than a quarter of COVID-19 cases shed infectious virus before the onset of symptoms. After isolation for 5 days from symptom onset, two-thirds of cases would still be infectious, but with reduced infectious viral shedding.7

Diagnosing COVID1

If a person has symptoms suggestive of COVID-19 infection, most people are no longer advised to get tested, and COVID-19 tests are no longer free for most people.

If a person is at highest risk of becoming seriously ill with COVID-19 infection: Advise to take a rapid lateral flow test as soon as possible, even if symptoms are mild. If the initial test result is negative, advise to do 3 rapid lateral flow tests over 3 days. The NHS resources on Testing for coronavirus (COVID-19) includes a link to order tests if eligible, interpreting and acting on test results.

If a person has a suspected or confirmed (tested positive) diagnosis of COVID-19, assess the person using face-to-face, telephone, or video consultations, depending on individualised risks and benefits using clinical judgement.

Assess for signs and symptoms suggesting severe illness and risk of early deterioration, such as:
Progressively worsening breathlessness; severe difficulty breathing or breathlessness at rest.

Consider reversible causes of breathlessness such as pneumonia, pulmonary oedema, pulmonary embolism, chronic obstructive pulmonary disease (COPD), and asthma, and manage appropriately.

  • Haemoptysis.

  • Cyanosis (blue lips or face).

  • Feeling cold and clammy with pale or mottled skin.

  • Collapse or syncope.

  • New confusion.

  • Drowsiness.

  • Reduced urine output.

Hypoxia (reduced oxygen saturation levels measured by pulse oximetry):

  • Oxygen levels of 92% or less in room air in adults (suggests severe hypoxia).

  • Oxygen levels greater than 4% lower than usual levels (suggests severe hypoxia).

  • Oxygen levels of 93–94% in room air in adults (suggests moderate hypoxia).

  • Oxygen levels below 91% in room air at rest in children and young people aged 17 years and under (suggests severe hypoxia).

Consider using 'exertion oximetry' tests (such as the 40-step walk and one-minute sit-to-stand tests) if oxygen saturation is at least 93% and the person is aged 65 years or more and/or at highest risk of serious illness, to assess for oxygen desaturation on exercise — a 3% or greater reduction in oxygen saturation level is considered significant.

If using a pulse oximeter at home, consider the use of the NHS England Self-monitoring COVID-19 diary which also provides information on how to use a pulse oximeter, recording and acting on results.

Some pulse oximeters may under- or over-estimate oxygen saturation levels, especially if the level is borderline. Levels may be over-estimated in people with dark skin.

COVID treatment1

If they are a household or overnight contact of a person who has had a positive COVID-19 test result, advise that it can take up to 10 days for infection to develop.

If suspected or confirmed COVID infection, arrange hospital admission if indicated following clinical assessment:

  • If severe hypoxia and/or severely ill, consider arranging urgent hospital admission.

  • If moderate hypoxia and not severely ill, consider arranging hospital assessment, the urgency depending on clinical judgement.

  • If hypoxia is a likely cause of breathlessness, consider arranging admission to secondary care.

  • Arrange hospital admission or specialist referral if there is a suspected complication, depending on clinical judgement.

If hospital admission is not clinically indicated:

  • If not at highest risk of becoming seriously ill with COVID-19 infection: Advise to try to stay at home and avoid contact with other people if they have a fever and/or they do not feel well enough to go to school, college, childcare, or work, or do their normal activities.

  • If a child has mild symptoms such as runny nose, sore throat, or mild cough and they feel well, they can continue to attend school, college, or childcare.

  • Advise the person to resume normal activities once any fever has settled and they feel better.

  • If confirmed COVID infection and hospital admission is not clinically indicated and an adult is not at highest risk of becoming seriously ill with COVID-19 infection:

    • Advise to try to stay at home and avoid contact with other people for 5 days after the day the test was taken.

    • Advise to avoid meeting people at higher risk of becoming seriously unwell from COVID-19, for 10 days after the day the test was taken.

  • If a child or young person aged under 18 years is not at highest risk of becoming seriously ill with COVID-19 infection, advise to try to stay at home and avoid contact with other people for 3 days after the day the test was taken.

Reassure that for most people symptoms resolve by 12 weeks.

Ensure any confirmed case of COVID-19 is notified to the local health protection team

General advice

  • Offer advice on living safely with COVID-19, including advice on getting vaccinated, ensuring adequate ventilation, basic rules of good hygiene, and when to consider wearing a face covering or face mask.

  • Offer mental health support if needed.

  • Offer advice on work, self-employment and benefits, and support at work.

Patients with a cough should be encouraged to avoid lying on their backs, if possible, because this may make coughing less effective. Cough should be initially managed using simple non-drug measures (such as honey). For cough that is distressing in a patient with COVID‑19, consider short-term use of a cough suppressant (such as codeine phosphate or morphine).

Patients with fever should be advised to drink fluids regularly to avoid dehydration, and to take antipyretics (such as paracetamol or ibuprofen) as appropriate (whilst both fever and other symptoms that antipyretics would help treat are present).

If confirmed COVID infection, antibody and antiviral treatments may be offered in the community if the person is aged over 12 years, and is symptomatic and not improving. NHS England provides information for COVID-19 community-based treatments.8

Hospital treatments

NICE currently recommends the following hospital treatments:2

  • Consider awake prone positioning for people in hospital with COVID-19 who are not intubated and have higher oxygen needs.

Non-invasive respiratory support

  • Do not routinely offer high-flow nasal oxygen as the main form of respiratory support for people with COVID-19 and respiratory failure in whom escalation to invasive mechanical ventilation would be appropriate.

  • Consider continuous positive airway pressure (CPAP) for people with COVID-19 when:

    • They have hypoxaemia that is not responding to supplemental oxygen with a fraction of inspired oxygen of 0.4 (40%) or more, and

    • Either escalation to invasive mechanical ventilation would be an option but it is not immediately needed, or

    • It is agreed that respiratory support should not be escalated beyond CPAP.

  • Consider using high-flow nasal oxygen for people when:

    • They cannot tolerate continuous positive airway pressure (CPAP) but need humidified oxygen at high flow rates.

    • Maximal conventional oxygen is not maintaining their target oxygen saturations and they do not need immediate invasive mechanical ventilation or escalation to invasive mechanical ventilation is not suitable, and CPAP is not suitable.

    • They need a break from CPAP (such as at mealtimes, for skin and pressure area relief, or for mouth care), they need humidified oxygen or nebulisers (or both), or weaning from CPAP.

Antivirals

  • Nirmatrelvir plus ritonavir is recommended as an option for treating COVID-19 in adults, only if they do not need supplemental oxygen for COVID-19 and have an increased risk for progression to severe COVID-19.

  • Consider a 3-day course of remdesivir for children and young people who weigh at least 40 kg and adults with COVID-19 who do not need supplemental oxygen for COVID-19, are within 7 days of symptom onset, and are thought to be at high risk of progression to severe COVID-19.

  • Consider a course of remdesivir (up to 5 days) for people who have COVID-19 pneumonia, and are in hospital and need low-flow supplemental oxygen.

  • Consider a 5-day course of molnupiravir for adults with COVID-19 who do not need supplemental oxygen for COVID-19, are within 5 days of symptom onset, and are thought to be at high risk of progression to severe COVID-19.

  • Sotrovimab is recommended as an option for treating COVID-19 in adults and young people aged 12 years and over and weighing at least 40 kg, only if they do not need supplemental oxygen for COVID-19, they have an increased risk for progression to severe COVID-19, and nirmatrelvir plus ritonavir is contraindicated or unsuitable.

  • Tocilizumab is recommended as an option for treating COVID-19 in adults who are having systemic corticosteroids, and need supplemental oxygen or mechanical ventilation.

  • Consider baricitinib for people 2 years and over in hospital with COVID-19 who need supplemental oxygen for COVID-19, are having or have completed a course of corticosteroids such as dexamethasone, unless they cannot have corticosteroids, and have no evidence of infection (other than SARS-CoV-2) that might be worsened by baricitinib.

Editor's note

Dr Krishna Vakharia, 14th May 2024

Remdesivir and tixagevimab plus cilgavimab for treating COVID-19 9

NICE has recommended remdesivir as an option for treating COVID‑19 in hospitals:

In adults - if they have a high risk of serious illness - see reference.
In babies, children and young people - if they are aged 4 weeks to 17 years and weigh at least 3 kg, and have pneumonia, and need supplemental oxygen, or if they weigh at least 40 kg, and have a high risk of serious illness - see reference.

NICE has not recommended tixagevimab plus cilgavimab for treating COVID‑19 in adults who do not need supplemental oxygen and who have an increased risk of progression to severe COVID‑19.

Corticosteroids
Offer dexamethasone, or either hydrocortisone or prednisolone when dexamethasone cannot be used or is unavailable, to people with COVID-19 who need supplemental oxygen to meet their prescribed oxygen saturation levels, or have a level of hypoxia that needs supplemental oxygen but who are unable to have or tolerate it. Continue corticosteroids for up to 10 days unless there is a clear indication to stop early, which includes discharge from hospital or a hospital-supervised virtual COVID ward.

Other treatments include prophylaxis of venous thromboembolism, the use of antibiotics only if there is evidence of additional bacterial infection and management of complications as applicable.

Offer management for any symptoms such as breathlessness, cough, anxiety, and agitation.
Assess and treat any underlying or reversible causes of symptoms, such as hypoxia, metabolic or electrolyte imbalance, co-infections, uncontrolled pain, urinary retention, and constipation.

Consider prescribing a benzodiazepine first-line to manage anxiety or agitation in people aged over 18 years. Seek specialist advice for people aged under 18 years.

Treatments for managing anxiety, delirium, and agitation in people aged over 18 years:

  • Anxiety or agitation and able to swallow: lorazepam tablets.

  • Anxiety or agitation and unable to swallow: midazolam injection.

  • Delirium and able to swallow: haloperidol tablets.

  • Delirium and unable to swallow: levomepromazine injection.

Midazolam and levomepromazine do not currently have a UK marketing authorisation for this indication or route of administration.

Prognosis1

  • The prognosis of COVID-19 infection varies depending on the person's age, ethnicity, comorbidities as well as the circulating variant.

  • Most people with COVID-19 infection will have a mild-to-moderate respiratory illness and will recover without needing specialist treatment.

  • People in highest risk clinical subgroups are more likely to develop more serious illness or complications.

  • In the UK, seroprevalence studies have shown an increased infection fatality ratio in older age-groups.

COVID vaccine10

Since the COVID‑19 vaccination programme was initiated in December 2020, the majority of adults in the UK have been vaccinated, and most of the adult and child population have also been naturally infected.

Vaccination against COVID‑19 provides modest but short-term protection (lasting a few months) against infection and mild symptomatic disease, and transmission. Protection against severe disease and death appears to be greater and maintained over the medium term.

COVID‑19 vaccines are an area of ongoing research and recommendations may change as more data and other vaccines become available.11

Primary immunisation

  • All adults, and children who were aged 5 years and over on or before 31st August 2022, are eligible for a primary vaccination course.

  • Children who reached the age of 5 years on or after 1st September 2022 are only eligible for vaccination if they are in a clinical at-risk group or are a household contact of an immunosuppressed individual.

  • Children aged 6 months to 4 years are also eligible for a primary vaccination course if they are in a clinical at-risk group.

In individuals with confirmed COVID‑19 infection, vaccination should ideally be deferred until clinical recovery. However, during care-home outbreaks, residents with confirmed COVID‑19 infection may receive the vaccine provided they are clinically stable. Ideally vaccination of adults and children at highest risk of serious illness should be deferred until clinical recovery and at least 4 weeks after onset of symptoms or 4 weeks from the first positive PCR result, depending on clinical judgement.

In patients with prolonged COVID‑19 symptoms, consider deferring the vaccine if the patient is seriously debilitated, under active investigation or has recently deteriorated, to avoid incorrect attribution of any change in symptoms to the vaccine.

Most eligible individuals should receive 2 doses of COVID-19 vaccine for their primary course. 3 doses are required for individuals aged 6 months and over who were severely immuno-suppressed at the time of their vaccination.

For most individuals, the Joint Committee on Vaccination and Immunisation (JCVI) recommends a minimum 8 week interval between doses, unless rapid immunisation is required in specific circumstances (eg, individuals about to receive immunosuppressive treatment). However, for healthy individuals aged under 18 years who are not health and social care workers, carers, or household contacts of immunosuppressed individuals, a minimum 12 week interval between doses is recommended.

The same COVID‑19 vaccine should ideally be used for the entire primary course, where possible. If the same vaccine is not available or suitable, or if the first product received is unknown, a suitable available product should be given to complete the primary course. If the course is delayed, it should be resumed, but the previous dose should not be repeated.

Vaccine choice for the primary course

  • Children aged 6 months–4 years: mRNA monovalent Comirnaty® COVID-19 vaccine is recommended.

  • Children aged 5–11 years: mRNA monovalent Comirnaty® or bivalent paediatric Comirnaty® Original/Omicron BA.4/5 COVID-19 vaccine is recommended. Although the mRNA monovalent Spikevax® vaccine is licensed for use in children aged 6 years and over, Comirnaty® preparations are preferred due to a lower reported rate of myocarditis.

  • Children aged 12–17 years: mRNA bivalent Comirnaty® Original/Omicron BA.4/5 COVID-19 vaccine is recommended. If this is unavailable, the bivalent Comirnaty® Original/Omicron BA.1 or monovalent Comirnaty® vaccine may be used. Although the mRNA Spikevax® vaccines are licensed for use in this age group, Comirnaty® preparations are preferred due to a lower reported rate of myocarditis.

  • Aged 18 years and over: the mRNA bivalent Comirnaty® Original/Omicron BA.4/5 or Spikevax® Original/Omicron BA.4/5 COVID-19 vaccine is recommended. If these are unavailable, the bivalent Comirnaty® Original/Omicron BA.1 or Spikevax® Original/Omicron BA.1 vaccine, or the monovalent Comirnaty® or Spikevax® vaccine may be used. In those aged 65 years and over, VidPrevtyn Beta® may also be used.

When a mRNA vaccine is considered unsuitable, Nuvaxovid® may be used for primary vaccination of individuals aged 12 years and over, or in those aged 65 years and over, VidPrevtyn Beta® may be used.

Individuals with immunosuppression and HIV infection (regardless of CD4 count) are considered at-risk. Individuals with severe immunosuppression may have an inadequate immune response to a primary course of vaccination and may therefore remain at high risk.

JCVI advises that individuals aged 6 months and over who were severely immunosuppressed at the time of receiving their first or second dose of COVID‑19 vaccine, should be offered a third dose as part of their primary course (ideally at least 8 weeks after the second dose). Individuals aged 5 years and over with severe immunosuppression should also be offered booster doses to extend protection from their primary course.

As there is limited evidence on response to immunisation in individuals with immunosuppression, specialists may advise their patients on optimal timing of vaccine delivery based on the patient’s immune status, likely response to vaccination, risk of COVID‑19 and of exposure. Post-vaccination testing for individuals with severe immunosuppression may be considered by specialists managing their care; advice on whether further precautions are required to reduce their risk can then be given if appropriate.

There is limited evidence on the use of COVID‑19 vaccines as post-exposure prophylaxis or to prevent transmission during outbreaks. For vulnerable individuals who require direct protection during prolonged community outbreaks, advice on post-exposure management can be sought from local health protection teams.

Contraindications and cautions

There are few people who cannot receive the Pfizer BioNTech, Moderna, or AstraZeneca COVID-19 vaccines. If there is any uncertainty, seek specialist advice from the local immunisation or health protection team.

  • Do not give the same vaccine to people who have had a confirmed anaphylactic reaction to a previous COVID-19 vaccine.

  • If a person received AstraZeneca vaccine, an alternative vaccine may be given in any setting, with observation for 30 minutes.

  • If a person received an mRNA vaccine, seek specialist advice if there was a possible previous anaphylactic reaction.

  • If there has been a possible previous allergic reaction to any component of the COVID-19 vaccine, seek specialist advice.

  • Do not give the Janssen COVID-19 vaccine if the person has a history of confirmed thrombosis with thrombocytopenia syndrome after receiving the Janssen COVID-19 vaccine.

  • Postpone immunisation if a person is acutely unwell until they have fully recovered. This is to avoid wrongly attributing any signs or symptoms of acute illness (including COVID-19) to the adverse effects of the vaccine.

  • If a person has a minor illness without fever or systemic illness, immunisation should not be postponed.

Vaccination of a person who may be infected, asymptomatic, or incubating COVID-19 infection is unlikely to have a negative effect on the illness. Prolonged symptoms of COVID-19 is not a contraindication to COVID-19 vaccine. If there is evidence of current deterioration, vaccination may be deferred to avoid incorrectly attributing any change in the person’s underlying condition to the vaccine.

Editor's note

Dr Krishna Vakharia, 16th October 2023

A guide to the COVID-19 autumn programme12

Government guidance from September 2023 advises that if a person feels unwell, they should wait until they recover to get a vaccine.

There is now no need to wait 4 weeks after having had COVID-19, provided that person is well. They should not attend a vaccine appointment if they think they could be infectious to others.

Adverse effects

COVID-19 vaccines are black triangle drugs, and any adverse reactions should be reported to the Medicines and Healthcare products Regulatory Agency (MHRA) using the Coronavirus Yellow Card reporting site.

Common or very common potential adverse effects include:

  • Local injection site reactions, eg, pain, swelling, redness, tenderness; fatigue; headache; chills; myalgia; arthralgia; fever.

  • Lymphadenopathy (axillary, supraclavicular, or cervical areas on the same side to injection).

Rare or uncommon potential adverse effects include:

  • Myocarditis and pericarditis: onset typically within a week of an mRNA vaccine, mainly affecting people under 25 years of age, most cases mild and stable, and most cases recover spontaneously without medical treatment. Presenting symptoms may include new-onset and unexplained significant chest pain, tachycardia or tachypnoea, dyspnoea, palpitations, dizziness or syncope. If suspected, refer to an Emergency department if the person is acutely unwell, has severe symptoms, or is clinically unstable.

  • Vaccine-induced immune thrombocytopenia and thrombosis (VITT): has been reported after administration of the AstraZeneca vaccine. The majority of cases occur between 4 and 28 days following COVID-19 vaccine. Presents with unusual venous thrombosis, including cerebral venous sinus thrombosis, portal vein thrombosis, and sometimes arterial thrombosis. Symptoms may include new-onset severe headache, may be worse when lying down or bending over; may be associated with blurred vision, nausea and vomiting, speech disturbance, weakness, drowsiness, or seizures; new unexplained bruising or bleeding; breathlessness, chest pain, leg swelling, or persistent abdominal pain. If suspected, refer the person to an Emergency department, or arrange an urgent same-day full blood count (FBC) if not acutely unwell, and refer to an Emergency department the same day if thrombocytopenia is confirmed.

  • Guillain-Barré syndrome: very rarely reported within six weeks of AstraZeneca vaccination.

  • Capillary leak syndrome: very rarely reported within 4 days of AstraZeneca vaccination in people with a previous history of this condition.

  • Transverse myelitis: an adverse effect of the Janssen COVID-19 vaccine of unknown frequency.

  • Dizziness: an uncommon adverse effect of the Comirnaty vaccine.

  • Paraesthesia and hypoaesthesia: an uncommon adverse effect of the Vaxzevria vaccine.

  • Other adverse effects (unknown frequency) include heavy menstrual bleeding (Comirnaty, Spikevax), and cutaneous vasculitis (Vaxzevria).

Pregnancy and breastfeeding

If a woman is pregnant:

  • If over the age of 18 years, the Pfizer BioNTech or Moderna vaccines should be offered.

  • If under the age of 18 years, the Pfizer BioNTech vaccine should be offered.

  • If already received a dose of the AstraZeneca vaccine, she can complete the course with the same vaccine or an mRNA vaccine.

  • If a woman finds out she is pregnant after she has started a course of vaccine, she may complete vaccination during pregnancy, and should complete vaccination at the recommended interval.

If a woman is breastfeeding, there is no known risk associated with a non-live COVID-19 vaccine while breastfeeding.

COVID booster

Since spring 2023, a booster dose has no longer been offered to individuals who are not in a clinical at-risk or other high-risk group. During the spring 2023 booster programme, a booster dose was offered provided that there has been an interval of at least 3 months from the previous dose, to the following individuals:

  • Residents in care homes for older adults.

  • All individuals aged 75 years and over.

  • Individuals aged 5 years and over who are immunosuppressed.

Vaccine choice for booster doses

  • Children aged 5–11 years: the mRNA monovalent Comirnaty® or bivalent paediatric Comirnaty® Original/Omicron BA.4/5 COVID-19 vaccine is recommended.

  • Children aged 12–17 years: the mRNA bivalent Comirnaty® Original/Omicron BA.4/5 COVID-19 vaccine is recommended. If this is unavailable, the bivalent Comirnaty® Original/Omicron BA.1 or monovalent Comirnaty® vaccine may be used. If a mRNA vaccine is unsuitable, Nuvaxovid® may be used.

  • Aged 18 years–74 years: the mRNA bivalent Comirnaty® Original/Omicron BA.4/5 or Spikevax® Original/Omicron BA.4/5 COVID-19 vaccine is recommended. If these are unavailable, the bivalent Comirnaty® Original/Omicron BA.1 or Spikevax® Original/Omicron BA.1, or the monovalent Comirnaty® or Spikevax® vaccine may be used.

  • Aged 65–74 years in domiciliary settings: may receive VidPrevtyn Beta® if that would facilitate operational delivery. If a mRNA vaccine is unsuitable, Nuvaxovid® may be used.

  • Aged 65 years and over: VidPrevtyn Beta® may also be used.

  • Aged 75 years and over and for residents aged 65 years and over in care homes for the elderly: mRNA bivalent Comirnaty® Original/Omicron BA.4/5 or Spikevax® Original/Omicron BA.4/5, or the VidPrevtyn Beta® COVID-19 vaccine is recommended. If these are unavailable, the bivalent Comirnaty® Original/Omicron BA.1 or Spikevax® Original/Omicron BA.1, or the monovalent Comirnaty® or Spikevax® vaccine may be used. If a mRNA vaccine is unsuitable, Nuvaxovid® or VidPrevtyn Beta® may be used.

Individuals who participated in a COVID‑19 vaccine clinical trial should have been provided with written advice by their clinical trial investigators about vaccination in the routine programme.

Further reading and references

  1. Coronavirus - COVID-19. NICE Clinical Knowledge Summary (CKS). Last revised March 2023.
  2. COVID-19 rapid guideline; NICE guideline [NG191]. Last updated June 2023
  3. Investigation of SARS-CoV-2 variants: technical briefings; GOV.UK.
  4. UK summary of coronavirus cases; UK Health Security Agency (HSA).
  5. Coronavirus (COVID-19) Dashboard; World Health Organization (WHO).
  6. COVID-19; Office for National Statistics.
  7. Hakki S, Zhou J, Jonnerby J, et al; Onset and window of SARS-CoV-2 infectiousness and temporal correlation with symptom onset: a prospective, longitudinal, community cohort study. Lancet Respir Med. 2022 Nov;10(11):1061-1073. doi: 10.1016/S2213-2600(22)00226-0. Epub 2022 Aug 18.
  8. COVID-19 community-based treatments; NHS England.
  9. Remdesivir and tixagevimab plus cilgavimab for treating COVID-19; NICE Technology appraisal guidance, May 2024
  10. COVID-19 - SARS-CoV-2: The Green Book, Chapter 14a; UK Health Security Agency (last updated April 2023).
  11. COVID-19 vaccination programme; GOV.UK. Last updated July 2023.
  12. A guide to the COVID-19 autumn programme; UK Health Security Agency, September 2023.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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