The lukewarm pace of coronavirus vaccination in the United States has led many policymakers and private employers to impose vaccine mandates, sometimes going so far as to refuse any religious or philosophical exemptions. Others, such as some universities and school districts, have opted for a softer approach — urging vaccinations, but not requiring them, in hopes that enough people will independently decide to do the right thing.
Unfortunately, neither approach is grounded in evidence. A substantial and expanding body of research suggests that mandatory immunizations work, but only if they strike a middle ground that avoids draconian measures but makes it inconvenient to opt out.
There is no question that vaccine mandates, crafted well, are effective. A review of studies from high-income countries showed that school immunization requirements were on average associated with 18 percentage points higher rates of routine childhood vaccinations. Similarly, during and soon after the H1N1 pandemic in 2009 and 2010, vaccination mandates were instrumental in increasing health care worker influenza immunization rates.
Most immunization mandates allow exemptions based on religious or other reasons. For instance, people with a history of severe allergies to vaccine components may be medically exempt from mandates. Some who say their faith doesn’t permit them to get vaccinated may get a religious exemption. However, if it is too easy to opt out, mandates are not as effective. In a 2012 study, my colleagues and I found that states with easy exemption procedures had more than twice as high vaccine refusal rates compared with states with difficult procedures.
But there is also a danger in making the mandates too strict. Several governments have tried to eliminate all nonmedical exemptions with the idea that most people won’t be able to opt out. The problem with that approach is that there is no simple linear relationship between the strictness of a mandate and vaccination rates.
In 2015, after a wave outbreaks — including a widely publicized outbreak of measles, initially identified at Disneyland, that led to more than 300 cases — California stopped granting vaccination exemptions to schoolchildren unless it was related to a medical issue. The state had also recently cracked down on a school admission process called “conditional entrants,” which was supposed to be for children who had begun getting their required vaccinations but had not completed the immunization course by the start of school. Vaccine-averse parents had abused the program.
The percentage of California children behind on their vaccines declined from approximately 10% in 2013 to almost 5% in 2017. But this decline was mainly due to the crackdown on the conditional entrant option, not a result of eliminating nonmedical exemptions.
Most parents with strong objections to vaccination — who would have previously sought nonmedical exemptions — found loopholes, such as acquiring medical exemptions, moving their children to home schooling or enrolling them in an independent study program.
Mandates may not be “nudges” in terms of the conventional use of the word, but effective mandates work by ensuring that it is far more convenient to receive the vaccine than not to — without taking away the choice of opting out altogether.
For example, when Washington state started requiring that all parents seeking nonmedical exemptions obtain mandatory health care-provider counseling and sign an “informed declination” form, vaccine refusal declined by more than 40%.
Based on vaccine ethics and science, my colleagues and I came up with six criteria for triggering coronavirus vaccine requirements. Among other things, we stipulate that mandates should be implemented only when the virus is not adequately contained and voluntary vaccination uptake has fallen short.
Under these criteria, the use of mandates is justified in specific settings in the United States, including hospitals, universities, many workplaces and the military. Since vaccine access has been sparser for many communities — particularly communities of color — a general mandate that covers everyone, or all adults, is not justified at this moment.
These mandates should include exemptions for religious and medical reasons. However, getting an exemption should not be easier than getting vaccinated. And having a mandate does not absolve governments of other responsibilities related to ensuring equitable vaccine access, such as engaging with the community and removing financial and logistical barriers to vaccination.
Mandates must never be vindictive; they should not be an outlet for the collective frustrations of the vaccinated. Instead, vaccine requirements that work as behavioral interventions can be a useful nudge to ensure that as many people as possible are inoculated against this deadly virus.
Saad B. Omer is director of the Yale Institute for Global Health and a professor at the Yale University schools of medicine and public health.
