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We know vaccines have been a miracle . Now,  led by the World Health Organization has found vaccines have saved an estimated  in the past 50 years from 14 different diseases. Most of these have been children under five, and around two-thirds children under one year old.

In 1974 the World Health Assembly launched the  with the goal to vaccinate all children against diphtheria, tetanus, pertussis (whooping cough), measles, polio, tuberculosis and smallpox by 1990. The program was subsequently expanded to include several other diseases.

The modelling, marking 50 years since this program was established, shows a child aged under ten has about a 40 percent greater chance of living until their next birthday, compared to if we didn’t have vaccines. And these positive effects can be seen well into adult life. A 50-year-old has a 16 percent greater chance of celebrating their next birthday thanks to vaccines.

The researchers developed  which took in vaccine coverage data and population numbers from 194 countries for the years 1974–2024. Not all diseases were included (for example smallpox, which was eradicated , was left out).

The analysis includes vaccines for 14 diseases, with 11 of these included in the Expanded Programme on Immunization. For some countries, additional vaccines such as Japanese encephalitis, meningitis A and yellow fever were included, as these diseases contribute to major disease burden in certain settings.

The models were used to simulate how diseases would have spread from 1974 to now, as vaccines were introduced, for each country and age group, incorporating data on increasing vaccine coverage over time.

Since 1974, the rates of deaths in children before their first birthday has more than halved. The researchers calculated almost 40 percent of this reduction is due to vaccines.

The effects have been greatest for children born in the 1980s because of the intensive efforts made globally to reduce the burden of diseases like measles, polio and whooping cough.

Some 60 percent of the 154 million lives saved would have been lives lost to measles. This is likely due to its ability to spread rapidly. One person with measles can spread the infection to .

The study also found some variation across different parts of the world. For example, vaccination programs have had a much greater impact on the probability of children living longer across low- and middle-income countries and settings with weaker health systems such as . These results highlight the important role vaccines play in promoting .

Low or declining vaccine coverage can lead to epidemics which can .

Notably, the COVID pandemic saw an overall decline in , with 86 percent of children having received their first dose in 2019 to 83 percent in 2022. This is concerning because very high levels of vaccination coverage ( percent) are required to achieve herd immunity against measles.

±õ²ÔÌý, the coverage for childhood vaccines, including measles, mumps and rubella, has declined compared to before the pandemic.

This study is a reminder of why we need to continue to vaccinate – not just against measles, but against  we have safe and effective vaccines for.

The results of this research don’t tell us the full story about the impact of vaccines. For example, the authors didn’t include data for some vaccines such as COVID and HPV (human papillomavirus). Also, like with all modelling studies, there are some uncertainties, as data was not available for all time periods and countries.

Nonetheless, the results show the success of global vaccination programs over time. If we want to continue to see lives saved, we need to keep investing in vaccination locally,  and globally.

The article was originally published in The Conversation as ,  written by Associate Professor Meru Sheel from the School of Public Health, ±¬ÁÏÍõ and Alexandra Hogan, UNSW Sydney. 

Hero image: CDC/ Pexels