COVID-19 Viral-vector Vaccine AstraZeneca, Janssen

Authored by , Reviewed by Dr Sarah Jarvis MBE | Last edited | Meets Patient’s editorial guidelines

The UK government and the Medicines and Healthcare products Regulatory Agency (MHRA) have granted temporary permission for this vaccine to be used for immunisation to prevent COVID-19 disease in individuals aged 18 years of age and over. Other countries have granted similar permission.

Use of the vaccine will be closely monitored to allow quick identification of new safety information. If you develop any side-effects, you can help this important process by reporting these to the dedicated COVID-19 vaccine monitoring scheme.

Please be aware that updates to safety information may happen frequently as new data become available. Please always refer to the manufacturer's printed information given to you at the time of your vaccination.

This vaccine may be offered to you as part of the UK's COVID-19 vaccination programme. People in other countries may receive this vaccine through their local programmes.

A healthcare professional will assess whether this vaccine is suitable for you before you are vaccinated. Ask your vaccinator if you have any questions or concerns.

The most common side-effects are tenderness, pain or bruising where the injection is given, generally feeling unwell, feeling tired (fatigue), chills or feeling feverish, headache, feeling sick (nausea), joint pain or muscle aches.

Ask a pharmacist to recommend a suitable painkiller in case you feel unwell, drink plenty of fluids and rest if possible.

Type of medicineCOVID-19 recombinant vector vaccine
Used forProtection against infection caused by SARS-CoV-2 virus
Also called'AstraZeneca' vaccine; 'Janssen' vaccine
Available asMulti-dose vials for injection

SARS-CoV-2 is a strain of coronavirus that first emerged in Wuhan, China, in late 2019. It has led to the worldwide COVID-19 pandemic. Social distancing measures, travel restrictions and use of personal protective equipment have been used to help control the spread of the virus. A number of vaccines are now available as part of national vaccination programmes.

The coronavirus has a distinctive 'spike' protein on its outer coat that it uses to infect host cells. Viral-vector vaccines use a weakened, genetically modified animal virus to deliver the genetic sequence for the spike protein into your body's cells. Your cells translate the genetic sequence and mass produce the coronavirus spike protein. 

These spike proteins trigger your immune system to create antibodies that will attack the SARS-CoV-2 virus if it enters your body. They also prime other parts of your immune system - your T cells - which provide longer-lasting protection against the virus. The vaccine does not contain coronavirus and cannot cause COVID-19 disease.

In clinical trials, the AstraZeneca vaccine was around 60-80% effective against COVID-19 disease from 14 days after the second dose. Effectiveness varied with the duration of the interval between doses; greater protection was achieved with dosing intervals of 9-12 weeks compared with 6-8 weeks. 

The Janssen vaccine requires only one dose and is, on average, 60-80% effective after 14 days. It is is more effective in adults aged over 65 years, reaching over 90% effectiveness in adults aged over 75 years.

The UK COVID-19 vaccination programme aims to protect the most vulnerable people from infection, such as the elderly and those with underlying health conditions, as well as frontline healthcare workers. The remaining population will be offered the vaccination based on age-related cohorts. You will receive one of a number of different vaccines available. Wherever possible, your second dose should be with the same vaccine as your first dose.

For information on other COVID-19 vaccines, see our leaflet for COVID-19 mRNA Vaccine (Pfizer BioNTech, Moderna).

Some vaccines are not suitable for people with certain conditions, and sometimes a vaccine may only be used if extra care is taken. For these reasons, before you are given COVID-19 viral-vector vaccine it is important that your vaccinator knows:

  • If you experienced a severe reaction, bleeding problems or an unwanted blood clot after your first dose of this vaccine.
  • If you are allergic to any of the ingredients in the vaccine as listed in the manufacturer's information.
  • If you have ever had a severe allergic reaction or breathing problems after any previous vaccination.
  • If you have ever had bleeding problems or a blood clot following treatment with heparin injections (a type of anticoagulant medicine).
  • If you have ever had a blood clot in the brain at the same time as low platelet levels.
  • If you are aged under 30 years and have not had this vaccine before.
  • If you currently have a severe illness with a high temperature (fever).
  • If you are pregnant, trying for a baby or breastfeeding (see below).
  • If you have a weakened immune system. This may be a result of an illness or taking medicines. You should still get vaccinated, but your immune response may not be as high as the general population's.
  • If you have a condition that makes you bleed more than is normal, such as haemophilia, or are taking anticoagulant medicines such as warfarin.
  • If you have recently been given any other vaccine.

COVID-19 vaccination if you are pregnant or breastfeeding

Initial trials of the vaccine did not include pregnant or breastfeeding women. As a result, in the early stages of the UK vaccination programme, it was recommended that women in these categories should discuss their personal risks with a healthcare professional.

However, it is now recommended that women who are pregnant, trying for a baby, or breastfeeding should be vaccinated in line with other people in their age or clinical risk group. This is because: 

  • There are now data from over 90,000 women vaccinated against COVID-19 with no safety concerns identified.
  • Pregnant women, particularly in the last trimester of pregnancy, may be at higher risk of complications of COVID-19 infection.

Because most of the women in these groups who have been vaccinated have received Pfizer BioNTech or Moderna vaccines, the UK recommendation is that they should be given one of these vaccines, rather than the AstraZeneca or Janssen vaccine.

  • Before you are given this vaccine, ask to read the manufacturer's printed information leaflet from inside the pack. The leaflet will give you more information about the vaccine and a full list of side-effects which you may experience from having it.
  • You will be given the vaccine by a trained vaccinator or healthcare professional. 
  • The vaccine is given by injection into a muscle, usually in your upper arm. If you have a condition or take medication that makes you bleed more easily than normal, let your vaccinator know.
  • You will need only one dose of the Janssen vaccine. It will take at least fourteen days after your dose before you get maximum protection against COVID-19 infection.
  • You will need two doses of the AstraZeneca vaccine given between 4 and 12 weeks apart. The second dose is important to boost your immunity and prolong its duration. It is not yet known if or when further booster doses may be needed.
  • Before receiving your second dose check to make sure it is the same vaccine as your first dose. If you have any questions, ask your vaccinator for advice.
  • If you have a high temperature (fever) or are acutely unwell at the time of a scheduled vaccination, you are advised to delay having the vaccine. You should arrange for an alternative appointment for the vaccination to be given.  A minor illness (such as a cough or cold) will not interfere with the vaccine.
  • Try to ensure you attend your appointment(s) for your vaccine dose(s). If you are unable to attend an appointment, cancel your unwanted appointment and book an alternative.
  • You are advised not to drive for the first 15 minutes after your vaccination, in case you begin to feel unwell. Do not drive if you feel dizzy, drowsy or otherwise unwell.
  • It will take at least 14 days after your second dose of AstraZeneca vaccine, or single dose of Janssen vaccine, before you get maximum protection against COVID-19 infection.
  • After you have been vaccinated, continue to follow any local restrictions or guidelines to help prevent the spread of COVID-19 infection.
  • Maintain hygiene measures such as routinely washing or sanitising your hands.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are planning to have, or have had the AstraZeneca or Janssen vaccine.

Along with their health benefits, most vaccines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with COVID-19 viral-vector vaccine. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common COVID-19 viral-vector vaccine side-effects (these affect more than 1 in 10 people)What can I do if I experience this?
HeadacheDrink plenty of water and ask a pharmacist to recommend a suitable painkiller. If the headache is severe and does not improve after taking a painkiller, seek medical advice
Itching, bruising, warmth, pain or tenderness at the injection siteAsk a pharmacist to recommend a suitable painkiller. Applying a cold compress may also help
Tiredness, feeling generally unwell, high temperature (fever), chillsDrink plenty of water and ask a pharmacist to recommend a suitable painkiller. Rest whenever possible
Feeling sick (nausea)Try to stick to simple meals, avoid spicy or fatty foods
Muscle and joint aches and painsAsk a pharmacist to recommend a suitable painkiller
Common COVID-19 viral-vector vaccine side-effects (these affect fewer than 1 in 10 people)What can I do if I experience this?
Being sick (vomiting), diarrhoeaDrink plenty of water to replace the lost fluids. Try to stick to simple meals, avoid spicy or fatty foods
CoughIf troublesome, ask a pharmacist to recommend a suitable remedy
Redness or swelling at the injection siteAsk a pharmacist to recommend a suitable painkiller. Applying a cold compress may also help

Important: extremely rare cases of blood clots with low levels of platelets have occurred after vaccination with COVID-19 viral-vector vaccines. The current UK reported rate of this event is just over 10 cases per million people vaccinated. The majority of cases occurred within the first three weeks after vaccination. The JCVI, MHRA and WHO have concluded that, for people aged over 40 years, the benefits of vaccination outweigh this small risk.

If you experience any of the following symptoms from around 4 days to 4 weeks after receiving a dose of viral-vector vaccine you should seek urgent medical advice:

  • A severe headache that is not relieved with simple painkillers or feels worse when you lie down or bend over.
  • A headache with blurred vision, drowsiness, confusion, difficulty speaking, muscle weakness or seizures (fits).
  • A rash with small, pin-prick bruises or bleeding under the skin (other than at the injection site).
  • Breathing difficulties, swollen legs, chest pain or tummy (abdominal) pain.

Some people have reported a sudden feeling of cold with shivering/shaking accompanied by a rise in body temperature, possibly with sweating, headache, muscle aches and feeling sick (nausea) or unwell, starting within a day of having the vaccine and usually lasting for a day or two.

If your fever is high and lasts longer than three days, or you have other persistent symptoms, speak with your doctor or a pharmacist.

Use of the vaccine will be closely monitored to allow quick identification of new safety information. If you develop any side-effects, you can help this important process by reporting these to the dedicated COVID-19 vaccine monitoring scheme.

  • You will not be asked to store this vaccine. The vaccination clinic must store the vaccine according to strict guidelines.
  • The vaccines can be stored in a monitored medicines refrigerator until use. Once removed from the refrigerator and opened, the vial must be used within six hours (AstraZeneca) or three hours (Janssen). The time of removal should be written on the vial. 

If you have any questions about this vaccine ask a pharmacist or your vaccinator.

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