Vaccines are one of the most powerful tools for substantially reducing mortality and are among the most cost-effective health interventions.
In addition to the direct protection provided to vaccinated individuals, high levels of vaccine coverage provide indirect protection (herd immunity) to the remaining unvaccinated individuals.
The World Health Organization (WHO) introduced the Expanded Program on Immunization in 1974. This program, which was supported by UNICEF and global donors, succeeded in providing substantial increases in routine childhood vaccine coverage: for example, global coverage of three doses of diphtheria-tetanus-pertussis (DTP3) vaccine increased from just over 20 percent in 1980 to over 75 percent in 1990.
The past two decades have seen further expansion of childhood vaccination programs in low- and middle-income countries (LMICs). But how well have they worked?
One research team tried to answer that. It sought to estimate deaths and disability-adjusted years (DALYs) averted through vaccination against 10 pathogens, in 98 LMICs.
Acquiring data from 2000 to 2020, researchers predicted a picture for:
Hepatitis B virus, Haemophilus influenzae type B, human papillomavirus, Japanese encephalitis, measles, Neisseria meningitidis serogroup A, Streptococcus pneumoniae, rotavirus, rubella and yellow fever.
Using demographic and vaccination coverage data, the impact of vaccination programs was determined by comparing model estimates from a scenario without vaccination with those from a scenario with vaccination.
Using mathematical models, the team estimated that vaccination would prevent 69 million deaths between 2000 and 2030, including 37 million between 2000 and 2019. Looking at the decade to 2019, this would have represented a 45 percent reduction in deaths compared to the scenario with no vaccination. Most of this impact is concentrated in a reduction in mortality among children under age 5, particularly from measles.
Increased vaccination coverage and the introduction of new vaccines in LMICs have had an important impact in reducing mortality. These public health benefits are expected to increase in the coming decades if progress in increasing coverage is sustained.
They also estimated that future increases in vaccine coverage and the introduction of additional vaccines will result in a 72 percent reduction in lifetime mortality in the 2019 birth cohort.
Source: THE LANCET
