Longer Interval Between First, Second COVID-19 mRNA Vaccine Dose Associated With Higher Antibody Levels


A longer interval between first and second doses of mRNA COVID-19 vaccines results in a stronger immune response, according to a study published in Clinical Infectious Diseases. The investigators compared blood test results from a total of 186 paramedics, some of whom received their second dose less than 4 weeks after receiving the first, whereas others received second doses after 6 to 7 weeks.

“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,” said Brian Grunau, MD, MHSc, assistant professor in the Department of Emergency Medicine at the University of British Columbia, in a press release.

According to the investigators, these findings have implications for the global vaccination effort. The study suggests that widening the recommended vaccine dosing interval could lead to a stronger long-term immune response in individuals. Further, it could also facilitate faster community-level access to the first vaccine dose.

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

Study participants are enrolled in COVID-19 Occupational Risks, Seroprevalence and Immunity among Paramedics, a national Canadian study examining the impact of the pandemic on paramedics. Though the study only began recruiting less than 10 months ago, investigators continue to provide data in real time in order to determine whether there are implications for policy decisions. The study authors said that this constant stream of information has been rewarding in terms of seeing public health efforts translate into clinically relevant findings.

“These results support the decisions across many jurisdictions in Canada for first doses fast with an extended dosing interval,” said Tim Evans, MD, DPhil, executive director of the COVID-19 Immunity Task Force of the Government of Canada, in the release.“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.”


Delaying second dose of mRNA COVID-19 vaccine produces stronger immune response [news release]. EurekAlert; December 1, 2021. Accessed December 1, 2021. https://www.eurekalert.org/news-releases/936456

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