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The Case against Vaccine Mandates for Domestic Flights


Recently, some have floated the idea that we ought to require proof of vaccination for domestic air travel. This policy, like other mandates, might raise the vaccination rate very, very slightly. Previously I estimated just a few percentage points for work-place mandates, and this action would have an even smaller effect at best. 

The benefit to this policy would be if it encouraged vulnerable, older people who do not have natural immunity to get vaccinated. Now let us consider the negative consequences. 

  1. The policy may inadvertently compel 2 or 3 doses of vaccination for people where there remains global uncertainty as to what dose and schedule is optimal. Men aged 12 to 30 face risks of myocarditis, which are mitigated if they are permitted to spread doses apart. Moreover, the optimal number of doses (1 vs. 2 vs. 3) remains unknown. Finally, the USA has not restricted use of Moderna (which has more myocarditis) unlike peer nations. Thus, such a policy may result in a 18 year old healthy man getting 3 doses of Moderna and experiencing myocarditis (aka net health suffering) just to board a flight to visit a dying loved one. These harms must be added to the ledger.
  2. If past is any predictor, the policy will have no way to consider natural immunity. Hundreds of millions of Americans have had COVID19. Compelling these people to get 2 or 3 doses to board a flight is unlikely to provide any benefit to anyone, and may even be detrimental (e.g. a 12 year old boy s/p natural immunity and 1 dose is now compelled to get dose 2). The policy will likely have no exemption for them, provoking outrage.
  3. This policy would further discriminate and alienate the unvaccinated. What they do instead of flying will have implications on the pandemic trajectory. They may seek and crowd other transportation (buses/ trains), which may drive short term spread and illness. (Long term, endemicity is inevitable)
  4. Checking vaccination status will require time at airports. The cumulative time lost will be massive. Just like removing shoes, this may continue for decades without re-appraisal. Billions in human capital will be spent.
  5. Policy is a long game. If you use political capital on marginal interventions that irritate the public, you may repeatedly lose re-election and be unable to make real differences in people’s lives in the future.
  6. There is no data this policy will keep airports/ planes safer. Very little data suggests airports/ planes are a major driver of spread, and moreover, the virus is endemic. Infection of all people is inevitable. The policy may only work to protect the unvaccinated, non-immune flying 80 year old from self-harm from exposure, but such an intrusive policy to accomplish this goal seems inconsistent with American values.

On balance, vaccine passports for domestic travel will have limited upside, and serious and unpredictable downsides. The policy may result in net harm to some fliers (young men compelled to receive second or third doses in short course). There is no way to know the gains will exceed downsides. This policy likely represents a failing attempt to ignore the truth: the virus is endemic, all people will be infected, and reinfected many times in their lives.

Republished from the author’s blog

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  • Vinay Prasad

    Vinay Prasad MD MPH is a hematologist-oncologist and Associate Professor in the Department of Epidemiology and Biostatistics at the University of California San Francisco. He runs the VKPrasad lab at UCSF, which studies cancer drugs, health policy, clinical trials and better decision making. He is author of over 300 academic articles, and the books Ending Medical Reversal (2015), and Malignant (2020).

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