Vaccines have extra effects – both good and badFor some years now doctors and scientists have been studying the effects of vaccines given to young children in Africa, not just on their ability to prevent a specific disease, but more generally on whether the child lived or died. Those children who had most recently received a vaccine against TB (the BCG vaccine) or a measles vaccine are less likely to die than those who had received no vaccines. What is more, the benefit was far greater than if the vaccines were preventing death just by preventing TB in measles; the vaccines seemed to be offering far greater benefits than this, probably by preventing deaths from other infections. However there was a flip side to this finding. Children whose most recent vaccine was the triple DTP (protecting against diphtheria, pertussis and tetanus) or the hepatitis B vaccine were far more likely to die than children who had not received any vaccines. Some vaccines appeared to be doing far more good than expected, saving more children's lives than anticipated, but other vaccines, including the widely used triple DTP vaccine, appeared to be actually doing more harm than good - actually killing children. For more on this please see my book Vaccines: A Parent's Guide or this page.
Up to now all this research into what has been called the "non-specific effects" of vaccination has been done in Africa where most children are relatively poorly nourished and live in far worse socio-economic conditions than children in the wealthier countries of the world. However a new study has now looked at this affect in children in Denmark. Because Danish children rarely die in infancy the researchers did not measure deaths, but instead measured the numbers of children who were admitted to hospital for any infection. They found that children who had received the triple MMR as the last vaccine had a reduced risk of hospital admission for infection over the subsequent months. Conversely those children who had received the five-in-one DTaP-IPV-Hib vaccine (similar to that used in the UK) had an increased risk of admission to hospital with infection. The reason for this could be that the MMR reduces the risk of serious infection in children, or it could be that the five-in-one vaccine increases the risk of infection in children, or it could be a combination of the two. Because children who had received no vaccines were not included in the study (possibly because there are so few in a country like Denmark) it is impossible to say. The five-in-one vaccine used in Denmark is very similar to Pediacel, the five-in-one vaccine given to children in the UK at 2, 3 and 4 months. Does this research imply that children are at increased risk of serious infection following their third five-in-one vaccine, given at four months of age in the UK, before being given the MMR at 12 to 15 months of age? Possibly, we just don't know. Perhaps unsurprisingly, the authors concentrate on the potential positive effect of the MMR vaccine, and avoid discussion of the potential negative effects of the five-in-one vaccine.
So how should this research influence our decisions on how to vaccinate our children? It may be sensible to give the MMR, or single measles vaccine, soon after the third DTaP containing vaccine. This is relatively easily done in the Scandinavian countries where the third DTaP containing five-in-one vaccine is not given until 12 months of age, but poses a problem in the UK where a third DTaP containing five-in-one vaccine is given as early as four months, earlier than in any other country in the world. The MMR, or single measles vaccine, is not usually given before 12 months of age. I will be taking account of these fascinating findings when drawing up individualised vaccine schedules at BabyJabs, my children's immunisation clinic. However this new research, important as it is, raises more questions than it answers. More research is urgently needed.
Added 28 Feb 2014