Vaccines work: Immunization has saved millions of lives worldwide

Between the years 2000 and 2019, vaccination programmes all over the world have averted around 50 million deaths, according to a recent study. In the coming decade, vaccines are expected to save 47 million more lives.

“Overall, our results provide a thorough assessment of the impact of vaccination activities prior to the novel coronavirus disease (COVID-19), from 2000 to 2019, and from 2020 thereafter,” the researchers said. “These results are subject to change as our understanding of the transmission and epidemiology of these pathogens continues to grow.”

“Additionally, future coverage, particularly during and following the pandemic, is uncertain. This study paints a picture of the immense progress to date and the tremendous health impacts that could be obtained over the next decade due to vaccination activities,” they added.

Twenty-one mathematical models were used to assess the impact of immunization against the following 10 pathogens: yellow fever, Streptococcus pneumoniae, rubella, rotavirus, Neisseria meningitidis serogroup A, measles, Japanese encephalitis, human papillomavirus, hepatitis B, and Haemophilus influenzae type B. Data and estimates were produced for 112 countries.

In the years between 2000 and 2100, the models showed a general decline in deaths attributable to each of the 10 pathogens as a result of vaccination. This effect varied by country, driven mostly by differences in vaccination coverage, health access, and other sociodemographic factors. [Elife 2021;10:e67635]

Stratifying by year, the researchers saw that vaccination activities from 2000 to 2030 for all 10 pathogens could avert 97 million (95 percent credible interval [CrI], 80–120) future deaths, corresponding to 5,100 million (95 percent CrI, 4,100–6,300) daily adjusted life-years (DALYs) averted.

In the years before the COVID-19 pandemic (2000 to 2019), vaccination drives have saved 50 million (95 percent CrI, 41–62) lives and averted 2,700 million (95 percent CrI, 2,200–3,500) DALYs. This suggests that the remaining deaths and DALYs averted could be attributed to the years during and after the pandemic, though changes to these figures are expected due to the impact of COVID-19 of access to healthcare, the researchers said.

“A global analysis of the impact of COVID-19 on vaccination activities is not yet available and it is unclear how the continued disruption, and likely impact of distributing a future SARS-COV-2 vaccine, will affect vaccination in the future. Conversely, we also do not know to what extent transmission has been perturbed due to nonpharmaceutical interventions instigated to mitigate COVID-19 for the pathogens mentioned here,” they said.

Since many of the pathogens in question are common among children, an analysis of vaccination impact in this population was also carried out. From 2000 to 2030, vaccines are estimated to avert 52 million (95 percent CrI, 41–69) deaths and 3,400 million (95 percent CrI, 2,700–4,600) DALYs in children under 5 years of age.

“Our study shows the substantial progress to date and as we look to the future, it continues to show the benefits of vaccination and motivates efforts to sustain and improve coverage of vaccination globally,” the researchers said.