Collateral Effects on Health

In patients with diabetes, influenza vaccination was associated with a reduced risk of all-cause death, cardiovascular death, and death from acute myocardial infarction (heart attacks) or stroke. The analysis included medical records from 241,551 adult patients in Denmark across nine consecutive influenza seasons (2007 to 2016). Influenza vaccination was associated with a reduced risk for being admitted to the hospital with diabetes-related complications, like diabetic ketoacidosis, hypoglycemia, or coma.

Key Evidence: Seizures are the most common non-gastrointestinal symptom associated with rotavirus infection. Studies have found that during the year following rotavirus vaccination the risk of childhood seizures were reduced by 18-21% for seizures requiring emergency care or hospitalization in the U.S. and by 16-34% for childhood seizures requiring hospitalization in Spain.

Key Evidence: Seizures are the most common non-gastrointestinal symptom associated with rotavirus infection. Studies have found that rotavirus vaccination significantly reduced the risk of childhood seizures during the year following vaccination by approximately 20% for seizures requiring emergency care or hospitalization in the US and by 16-34% for childhood seizures requiring hospitalization in Spain.

Key Evidence: This 2013 review summarizes data from several randomized trials in which measles and tuberculosis vaccines were associated with a substantial reduction in overall child mortality, which cannot be solely explained by prevention of the target disease. These studies suggest that in addition to disease-specific effects, some live vaccines may also provide “nonspecific effects” that enhance the immune system’s ability to protect against additional pathogens.

Key Evidence: In a study of data from England & Wales, Denmark, and the US, it was shown that measles infection suppresses the immune system for up to 3 years after infection, increasing the risk of death due to other childhood infections during that time. This means that prevention of measles significantly impacts overall health during critical childhood years.

Key Evidence: An analysis of children aged 12-59 months in rural India showed that children who were not vaccinated against measles vaccine in infancy had a three times higher likelihood of death, with unvaccinated children from lower caste households having the highest risk of mortality (odds ratio, 8.9). However, the results also revealed a nonspecific reducing effect of the vaccine on the overall child mortality in this region. This indicates that vaccination against measles can benefit the overall population, especially those in lower castes who have not received the vaccine in infancy. Thus, making them the group that would receive the highest benefit.

Key Evidence: Three randomized controlled trials enrolling a total of over 6500 infants over 12 consecutive years in Guinea-Bissau found a 38% reduction in all-cause neonatal mortality associated with early vaccination with BCG. Revisiting these trials to explore the seasonal variation in this effect, it was found that early vaccination with BCG was particularly beneficial when administered between November and January, coincident with peaking malaria infections.

Key Evidence: In a 2014 review of the non-specific effects of measles vaccines, among others, the WHO Strategic Advisory Group of Experts indicated that some studies of measles vaccine were suggestive (but not conclusive) of a beneficial effect of measles vaccine on overall mortality beyond the expected direct effect of the vaccine against measles. In particular, randomized control trials of children in Guinea- Bissau which looked at mortality up to the age of 9 months showed a low number of deaths post administration of the 3 doses of the measles vaccine over the study follow up period. Another trial in Nigeria also showed similar results.

Key Evidence: A study including thousands of children from the U.S. state of Texas found that children born in counties with high coverage of HepB, Polio, and Hib vaccines were 33%, 37%, and 42% less likely to develop a specific type of leukemia than children born in counties with lower coverage of each vaccine.