Dear doctor

Q: I am becoming nervous about vaccinating my baby. She is only a month old and I am already sceptical about MMR. But now I have heard that the injections they have at two, three and four months old contain mercury. Is it true and should I avoid them?

A: Immunisation has become such an emotive subject. It seems a shame that a public health programme that should be making us feel that our children are protected from a range of potentially life-threatening conditions engenders such anxiety. Each health scare not only makes us worried about a particular jab, but also undermines our confidence in the whole concept of mass immunisation.

Part of the reason for our scepticism is the success of the programme. We don't nurse children desperately ill with whooping cough, never hear of anyone dying of tetanus or diphtheria and don't see children in callipers or an iron lung because of polio-induced paralysis. So I would advise you to remain open-minded about immunisation in general, while exploring specific worries such as the mercury story.

Some childhood vaccines do contain low levels of a mercury derivative called thiomersal which acts as a preservative. Diphtheria, tetanus and pertussis (whooping cough) contain thiomersal, although MMR doesn't. In the US, thiomersal-containing vaccines have been phased out on the basis that there have been increased reports of autism and brain damage. There is no proven link between the vaccines and this increase.

The UK Committee on Safety of Medicines has recently reviewed all available evidence and concluded that there is no evidence that thiomersal-containing vaccines cause neuro-developmental problems. As I always say, where the US leads, we follow. So expect thiomersal-free vaccines within the decade despite all the official protestations of safety.

Every medical intervention, including immunisation, carries some element of risk. So does letting your child grow up unimmunised. Experts say the risk of being immunised is less than being unimmunised, and I tend to believe them.

Q: I am a very fit 56-year-old man. I'm now in a long-term relationship since my wife left me last year. I have been feeling a bit run down and a friend said I looked a bit yellow. My GP took a blood test and has now called me back to say I have hepatitis B. He asked me about other sexual encounters and the truth is that I did have a couple of homosexual encounters soon after my wife left me. I was a bit reluctant to talk about this because I haven't told my current girlfriend. Do you think I need to?

A: You need to tell your girlfriend that you have hepatitis B because it is sexually transmitted. Ideally, you should also try to contact your gay partners if you can, to tell them. You get hep B when infected blood, semen or saliva mixes with your blood. The commonest ways of catching it are anal sex or intravenous drug use. You can't catch it from kissing. Some people with hepatitis feel fine or a bit run down, as you do. Others feel ill, sick and have abdominal pains. The jaundice makes you look yellow. You will be advised to avoid alcohol until blood tests show that your liver has recovered from the infection.

In more than 90% of cases, the virus clears completely from your body, but 5-10% of sufferers have persistent infection and need long-term follow-up. You should go to a sexually transmitted infections clinic to be screened for other conditions and should urge all your recent partners to do so too. If they don't attend, whoever infected you may carry on infecting others. Avoid sex with your girlfriend until you are given the green light by the clinic. If you do have sex, use condoms.

· These answers are intended to be as accurate and full as possible, but should never be used as a substitute for seeking medical help. If you have a question for Dr Robinson, email drann@dircon.co.uk or write to her c/o The Health Editor, The Guardian, 119 Farringdon Road, London EC1R 3ER. She regrets that she cannot enter into personal correspondence.

Thanks to guardian.co.uk who have provided this article. View the original here.