Delaying 2nd COVID-19 vaccine dose produces stronger immune response

VANCOUVER, British Columbia — Still waiting to receive your second dose of the coronavirus vaccine? You might want to actually hold off even longer. Researchers from the University of British Columbia report that it may be beneficial to delay getting the second mRNA COVID-19 dose by another week or two. Study authors conclude a longer interval between doses leads to a stronger immune response.

Researchers analyzed and compared blood test results from 186 paramedics. Some of those individuals were fully vaccinated within the standard recommended timeframe of a few weeks to a month. However, others didn’t get their second COVID vaccine dose for six to eight weeks after their first shot.

“We found significantly higher levels of antibodies in individuals who had longer vaccine intervals, and this was consistent regardless of which mRNA vaccine was administered,” says Dr. Brian Grunau, an assistant professor in UBC’s Department of Emergency Medicine and a scientist at the Centre for Health Evaluation and Outcome Sciences, in a university release.

Both the Pfizer and Moderna vaccines are of the mRNA variety and require patients to get two doses for full protection. While antibody counts aren’t the only indicator of immune protection, it’s a major piece of the protective puzzle.

Will delaying doses lead to higher vaccination rates?

This work holds major implications as the world continues to combat the ongoing pandemic via mass vaccination. Despite major global efforts, roughly half of the planet’s population remain unvaccinated. Study authors believe that if the world adopts a policy of delaying the time between first and second doses, it would help speed up community-level access to first vaccine doses.

“This longer interval strategy enables early access to first doses in the population and ensuring the best protection possible with the two-dose series,” Dr. Grunau adds.

It’s also worth mentioning that this study did not investigate actual breakthrough infections among participants. Moreover, while the seemingly never-ending stream of new findings and discoveries in reference to COVID-19 and vaccination efforts can certainly be overwhelming and frustrating for health officials and the general public alike, study authors hope their work may help make a difference in the battle against COVID-19.

“That is the real goal of any researcher,” Dr. Grunau notes. “We want to do research that will actually positively impact people’s lives and affect policy.”

“These results support the decisions across many jurisdictions in Canada for first doses fast with an extended dosing interval,” concludes Dr. Tim Evans, CITF Executive Director. “The results are also very important in informing the roll out of vaccines in other countries where extending the dose interval may help to promote vaccine equity.”

The study appears in the journal Clinical Infectious Diseases.

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