Historical evidence to inform COVID-19 vaccine mandates

The best comparison to the massive global vaccination effort that is now starting might be the smallpox vaccination campaigns that culminated in the eradication of the disease, as detailed by Richard Horton.¹ With smallpox, vaccine mandates played a pivotal role in reducing mortality and case rates.

By the mid-19th century in Europe, regions with mandatory vaccination proved to have substantially fewer deaths from smallpox than those that relied on voluntary vaccination. In 1853, smallpox vaccination became compulsory in England. In the years before mandatory vaccination in England and Wales, there were more than ten times as many deaths per person than there were in the regions of Italy and Sweden where vaccination was manda­tory.² In German states, mandatory vaccination was introduced in 1874. In the 5 years before the mandate, smallpox mortality rates were more than 30 times higher than in the 5 years following the mandatory vaccination law. These results stood in contrast to neighboring countries with persistent mortality rates.³

Perhaps the clearest experiment with mandatory vaccination was in the USA, informed by the European experience with vaccine mandates decades earlier. The results were notable. Between 1919 and 1928, the ten states with mandatory vaccination laws had 6·6 cases per 10 000, the six states with local options for laws on vaccination had 51·3 cases per 10 000, the 28 states with no laws on vaccination had 66·7 cases per 10 000, and the four states where mandatory vaccination was prohibited had 115·2 cases per 10 000.³ Between the extremes of policy on vaccine mandates, there was a 20-times difference in smallpox case rates.

COVID vaccine hesitancy puts many communities at risk of not reaching the rates of vaccination needed to prevent future outbreaks, even if these communities succeed in solving the challenges of vaccine supply and distribution. In surveys, nearly half of the population in some countries stated a reluctance to be vaccinated. Populations mistrustful of the government, who are less educated, and who have lower incomes are most hesitant to be vaccinated.⁴

Most countries have a mandatory vaccination programme for childhood vaccinations, with varying strat­egies for enforcement that might establish precedent.⁵ If strategies of persuasion do not achieve adequate vaccination rates in our com­muni­ties, it needs to be considered whether vaccine mandates—coercive policies that are often a last resort—might be needed to bring this crisis to an end. With consideration to the potential implementation of these mandates, it is necessary to look to the most relevant data available, even if those data are from a century ago.

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