If vaccines come on the market that are less effective than existing vaccines against new variants of SARS-COV-2, should people get them or wait until more effective vaccines are available?


SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

This article was published on
February 3, 2021

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What our experts say

Context and background


Media briefing

Media Release

Expert Comments: 

Dave O’Connor, PhD

If your house is on fire, don’t wait until you have the perfect hose. People should get vaccinated with whatever effective vaccine they have access to because this will help protect themselves and their communities by impacting the global viral load. Continuing precautions like mask wearing and distancing even after you get vaccinated will have a much greater impact on how well the vaccine keeps you safe than which vaccine product you receive.

As their part of the bargain, scientists and policymakers need to evaluate ways of improving the protection offered by vaccines that might have lower predicted efficacy. For example, the single dose Johnson and Johnson vaccine has several logistical advantages but has a lower clinical trial efficacy than the mRNA vaccines. Studies that look to pair a dose of the Johnson and Johnson vaccine with a later dose of an mRNA vaccine once supply isn’t as constrained should be started right away. This will let those who do get a less effective response initially to eventually be boosted to the same levels of protection as those who receive the most effective vaccines from the outset.

Jiang Zhu, PhD

If the current vaccines become less effective against new variants but still reduce the symptoms of severe disease, that is a good enough reason to get vaccinated. However, if people who get vaccinated have a less effective immune response, that also increases the possibility of generating new and more evasive SARS-CoV-2 escape mutants.


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