Estimated number of reported vaccine-preventable disease cases averted following the introduction of routine vaccination programs in Sweden, 1910-2019.

Background: Routine childhood vaccination programs have had enormous positive public health impacts worldwide. However, in some areas, these benefits may be impeded by vaccine hesitancy and undervaccination. We estimated the number of reported cases of measles, pertussis, mumps and poliomyelitis averted in Sweden after the introduction of routine childhood vaccination programs.

Methods: We used annual national data on population size and the number of reported cases of measles (1911-2019), pertussis (1911-2019), mumps (1914-2019) and poliomyelitis (1910-2019) for Sweden. For each disease, we calculated the median and 95% confidence interval of the annual pre-vaccination incidence to estimate the number of counterfactual cases; that is, the estimated number of cases that would have been observed in the post-vaccination period had no vaccine been introduced (median incidence × average annual population). For the post-vaccination periods, we calculated reported cases averted and assumed all decreases were due to vaccines.

Results: In total, for all four diseases combined, over 2.1 million cases were reported over the respective surveillance periods. Since the introduction of vaccinations, we estimate that over 1.5 million reported cases of these four diseases combined have been averted: measles (633 091), pertussis (608 670), mumps (262 951) and poliomyelitis (58 240). However, due to underreporting, especially during pre-vaccination years, these are likely underestimates.

Conclusions: Since the introduction of these routine childhood vaccination programs in Sweden, a substantial number of reported cases of vaccine-preventable diseases have been averted. Vigilance against both failure to vaccinate and undervaccination is necessary to prevent future increases of these vaccine-preventable diseases.