Some vaccines used in the developing world may do more harm than goodYesterday over 4 billion dollars was pledged by world leaders to vaccinate children in the developing world against pneumococcal disease and rotavirus, two of the leading causes of death in children worldwide, causing pneumonia and gastroenteritis respectively.
Let us hope that this is money well spent and that the widespread introduction of these vaccines really does lower the burden of childhood mortality in developing countries.
The problem is that there is strong evidence that some of the most widely used vaccines in the developing world may actually be doing more harm than good.
The world vaccine community was shaken in 2000 when research was published which showed that children in Guinea-Bissau, given routine vaccinations, were more, rather than less, likely to die over the subsequent six months. Some other vaccines they received were clearly doing good. The measles vaccine appeared to be hugely beneficial, halving the chance of dying, whilst receiving a TB vaccine also reduced the chance of a baby dying by 28% during the six-month period following vaccination. But receiving either the triple DTP jab, or polio drops, increased the likelihood of death by between 38% and 84%.
Taking into account that vaccinated children were already likely to be better nourished, and living in more sanitary conditions, these findings became even more alarming. The World Health Organisation sent out two experts to Guinea-Bissau to investigate, but they were unable to find anything to invalidate the study. Instead they concluded that the results "demand an immediate response". Despite this WHO remained highly critical of the study and defended its vaccination policy. The study's Danish authors stood by their results, calling for urgent research into the effects of vaccinations in child mortality. Further research has since been undertaken - in Guinea-Bissau, Senegal, Gambia and the Congo - all of which verify the increase in death rate of children who'd been given the triple DTP vaccine. The primary consolation was the confirmation that the measles vaccine was saving lives.
Further disturbing news surfaced in 2004, with the publication of research into the effects of hepatitis B vaccine given to babies in Guinea-Bissau where, like in many other developing countries, the disease is a big health problem. Babies given the vaccine were twice as likely to die before their first birthday than children not given the vaccine. DTP and hep B are two of the most widely used vaccines around the world. If they are causing more deaths in the developing world than there preventing something is going seriously wrong.
The main evidence for success of widespread vaccination has come from observational data If cases, or deaths, from the disease fall after the introduction of a vaccine it is assumed that this has happened because of the vaccine. A trial, for example, from the Gambia showed an impressively large and rapid fall in Hib disease after the introduction of, and probably caused by, the vaccine. However a possible problem with this approach is shown by the experience of Nigeria. Following increased vaccination there was a drop in the numbers of measles and whooping cough cases but this drop was accompanied by similar falls in cases of chickenpox and dysentery for which no vaccines were given. This casts doubt on whether the decreases were caused by vaccination or whether they would have happened anyway.
I do not want to suggest that it is all bad news. Some vaccines offer unexpected benefits. This has been seen most often with measles immunisation which appears to offer children a 30% to 86% reduction in overall death rate, though those who survive natural measles infection also benefited from better survival than those who didn't catch measles.
Vaccination against TB has also been found to save more lives than expected solely from preventing TB, and that is in addition to its apparent ability to prevent leprosy.
I am not trying to argue against vaccination; after all I run an immunisation clinic for babies myself. The point I wish to make is that there is a lot that we do not understand about vaccination and mass immunisation is not necessarily always a good thing. We have to look at the evidence. Even if a vaccine is preventing cases of the disease, which it usually does, it is of no benefit if it is not actually saving lives.
By all means let us introduce vaccinations against pneumonia and diarrhoea around the world but let us also fund good research to ensure that these vaccines are ultimately doing more good than harm. After all there are other ways of preventing diarrhoeal diseases primarily by providing clean water; children around the world are more likely to receive vaccinations that have access to clean water and safe sanitation. Providing children with safe water and sanitation is completely free of side effects and would save the lives of over 1 1/2 million children.
Added 14 June 2011