Routine infant vaccines currently used in low income countries were not tested in randomized trials for their impact on overall child survival before their introduction. It has been assumed that the impact of a vaccine on mortality is proportional to the vaccine’s efficacy and the contribution of the target disease to overall mortality. The past 15 years of research on vaccines in low income countries, however, have shown that this assumption is not a tenable basis for vaccination policy, since vaccines have important non-specific effects. For example, measles and BCG vaccines have reported significant reductions in all-cause mortality, while Diphtheria-tetanus-pertussis (DTP) and high-titre measles vaccine has been associated with increased mortality, especially in girls.
The study was conducted in Guinea-Bissau to determine whether BCG revaccination at 19 months of age reduces overall child mortality. The trial was stopped prematurely because of a cluster of deaths in the BCG arm of the study. The hazard ratio for BCG revaccinated children compared with controls was 2.69.
The authors believed that this was not related to the BCG vaccinations itself, but to the DTP vaccine, which effect is somehow negatively altered by BCG, and to iron and vitamin A supplements that the children received during the experiment.
Due to the fact that in Guinea-Bissau children were vaccinated once in three months, it turned out to be a natural experiment. Some children have already been vaccinated by the age of 3-5 months, and some haven’t.
The risk of death in children vaccinated against diphtheria/tetanus/pertussis (DTP) was 10 times higher than that of the unvaccinated children. Children who were also vaccinated against poliomyelitis (OPV) died only 5 times more often that the unvaccinated children.
After vaccination started, infant mortality at the age over 3 months increased by 2 times.
The author of the study concludes that the vaccine against diphtheria/tetanus/pertussis kills more children than it saves.
The authors can hardly be accused of being anti-vaccination. Peter Aaby, one of the authors of the study, created Bandim Health Project in Guinea-Bissau, one of the main goals of which is to vaccinate children.
Children from Guinea-Bissau, who received a diphtheria/tetanus/pertussis vaccine together with the measles vaccine died twice more often that those who only received a measles vaccine.
Authors cite several more studies with the same results in Gambia, Malawi, Congo, Ghana and Senegal.
Children who received a pentavalent vaccine (diphtheria/tetanus/pertussis/Hib/hepatitis B), in addition to measles and yellow fever vaccines, died 7.7 times more often than the children who did not receive a pentavalent vaccine.
In this lecture Susan Humphries explains why the combination of live and killed vaccines leads to this effect.
A meta-analysis of three studies in Guinea-Bissau. Among those vaccinated with DTP, the mortality rate was twice as high comparing to those who were not vaccinated. The ratio was higher for girls. In addition, unvaccinated children were usually too sick or too weak to receive the vaccine, and their nutrition was poorer. They more often lived in rural areas where child mortality was generally higher. Therefore, the authors write, the negative effect of vaccination in these studies is underestimated.
There is no prospective study showing that DTP vaccination is associated with reduced mortality. Moreover, over the past 20 years, several studies have found that DTP is associated with higher mortality, especially among girls. However, three-dose coverage of this particular vaccine is used as a key indicator of the success of vaccination programs. Given that all studies, including the present one, suggest that DTP is associated with increased female mortality, this is really an illogical position. We need to use program performance indicators which are positively associated with better child survival.
WHO experts have argued that the negative effect of DTP is exaggerated, because studies have only been conducted in situations with herd immunity against pertussis and where the benefit of preventing pertussis would not be seen. However, pertussis was endemic in the 1980s before the roll out of the vaccination program in Guinea-Bissau, but all three studies of the introduction of DTP into urban and rural areas of Guinea-Bissau showed excess mortality associated with DTP vaccination.
In Guinea-Bissau among children who had measles, allergies were 3 times less common than in vaccinated children who did not have measles. They also had dust mite allergy 5 times less often.
This is explained by the fact that measles virus stimulates cellular immunity, while humoral immunity is responsible for allergies.
Children who were breast-fed for more than a year, and children in whose houses pigs lived, also suffered from allergies less often. Judging by indirect evidence, infections protect against allergies only if the infection occurs at an early age. Most likely, the reaction of T cells to allergens matures until 5-7 years of age, and until that time it changes under the influence of environmental factors, such as infections.
In another study, measles or whooping cough before the age of three years was associated with a reduced risk of asthma.
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