Increases in vaccine coverage and the introduction of new vaccines into LMICs have had a major impact in reducing mortality. Vaccination programs for ten selected pathogens will have averted an estimated 69 million deaths in 98 low- and middle-income countries between 2000 and 2030. Most of this impact has been concentrated in a reduction in mortality among children younger than 5 years (57% reduction), most notably from measles. These public health gains are predicted to increase in coming decades if progress in increasing vaccine coverage is sustained.
Health
Immunizing pregnant women protects infants from influenza, with 56% efficacy in the first 2 months of life
A pooled analysis of three randomized controlled trials conducted in Nepal, Mali, and South Africa between 2011 and 2014 found that immunization during pregnancy provided protection against influenza to young infants from birth through 4 months of age. Protection against infant influenza was greatest in the first 2 months of life, with 56% efficacy, and the pooled efficacy of maternal vaccination to prevent infant laboratory-confirmed influenza up to 6 months of age was 35%.
Influenza vaccination in patients with diabetes reduces the risk of death and complications
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.
The introduction of the dTpa vaccine for pregnant women in Brazil reduced pertussis hospitalizations in infants
In response to an increase in pertussis cases beginning in 2010, Brazil introduced dTpa vaccine into the national immunization schedule for pregnant women in 2013. In the pre-maternal vaccination period (2011–2013), the average annual incidence of pertussis hospitalizations in children under 1 year old was 98.3/100,000 and in the post-maternal vaccination period (2015–2017) the average was 65.9/100,000, a decline of 32.9%.
A study in Germany found that vaccinating children against influenza reduces infections in the general population
A modelling simulation study in Germany found that routine influenza vaccination coverage of 55% in children of 6 months to 17 years indirectly reduces influenza infections by 26% in the general population through pronounced herd effects. The study authors conclude that targeting children in influenza vaccination campaigns may not only reduce their individual disease burden, but also that of non-vaccinated individuals.
Vaccinating both boys and girls against HPV can eradicate cancer-causing types of the virus
A Swedish-Finnish study conducted between 2007-2014 found that vaccinating both girls and boys against HPV (a gender-neutral vaccination strategy) could lead to the eradication of the most common cancer-causing types of the virus through stronger herd immunity. The study randomized HPV vaccination interventions across 33 towns (gender neutral HPV, girls-only HPV, and a control non-HPV vaccination), including 80,000 adolescents between ages 12 and 15. Results of general HPV screening at the age of 19 showed that gender-neutral vaccination prevented HPV infections much more effectively than vaccinating girls only.
Immunization can reduce child mortality and enhance the immune system’s ability to fight against other diseases
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.
Administration of vaccines can also decrease childhood deaths from other causes, above and beyond the expected direct impact of the vaccine
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.
Influenza vaccine for pregnant women in Bangladesh led to fewer respiratory illnesses in their infants
Pregnant women in Bangladesh who received the influenza vaccine had elevated levels of anti-influenza antibody in their breast milk. The infants of mothers who received the vaccine during pregnancy had fewer episodes of respiratory illness with fever than the infants of mothers who did not receive the influenza vaccine during pregnancy. Further, exclusive breastfeeding was found to have a protective effect against respiratory illness with fever in infants.
Immunization during pregnancy can increase anti-meningococcal antibodies in breastmilk, providing better protection for infants
The breastmilk of mothers in Bangladesh who received the meningococcal vaccine during pregnancy had anti-meningococcal antibody levels at 3-6 months after delivery of four to five times higher than that of mothers who did not receive the vaccine.
Although this study was published in 2002, the data on this topic are sparse as it is methodologically difficult to conduct studies to evaluate the relationship between anti-meningococcal antibodies in breastmilk and protection.