Longer gaps between mRNA vaccine doses lead to stronger immune response: Canadian study

A new canadian study found that delaying the second dose of a mRNA vaccine for COVID-19 creates a stronger immune response than two doses given closer to each other.

The peer-reviewed study compared the blood test results of 186 paramedics across the country, 118 of whom were doubly vaccinated with less than four weeks between doses, and 68 of them waited between six and seven. weeks for a second injection.

Regardless of the mRNA vaccine was used – Pfizer-BioNTech’s Commirnaty, Modern Spikevax or a combination of the two – those who waited longer had higher antibody concentrations.

Antibody are proteins produced by the immune system that circulate in the blood, recognize foreign substances such as bacteria and viruses and neutralize them.

“I think for people who are not yet vaccinated, this is very important,” Dr Brian Grunau, lead researcher of the study, said in an interview.

“We believe that the immune response generated by a vaccine – a strong response is likely to be able to better fight off a Covid infection. “

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The study, funded by the federal government COVID-19 Immunity Working Group, was published on Tuesday in the journal Clinical infectious diseases. Its findings, however, were analyzed in July and shared with the task force and other public health decision makers.

This is the first peer-reviewed study in North America examining the time between the first and second dose of mRNA vaccines, according to a press release from the University of British Columbia, where Grunau teaches emergency medicine.

He said the results are also important for countries that have not had stable access to vaccines – delayed intervals mean not only more antibodies, he explained, but more time to get vaccinated more. of people.

The study did not assess “breakthrough” COVID-19 infections – infections that occur after full immunization.

Vaccination intervals have varied in immunization programs across Canada as new data has emerged, and factors such as epidemics and patient vulnerability impact the need to get people immunized twice quickly.

In August, for example, the Government of British Columbia is reducing the interval between vaccine doses of seven weeks to four weeks for about 170,000 people living in areas of virus outbreaks.

The National Advisory Council on Immunization (NACI) recommended wait eight weeks between doses, but cites four weeks as the minimum acceptable.

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Other studies have also shown that increased intervals between doses of mRNA vaccine can produce stronger immune responses.

A British study of the 503 health workers who received two injections of the Comirnaty vaccine had similar results – levels of neutralizing antibodies were twice as high after a longer dosing interval. His findings were released in July, around the same time Grunau and his colleagues were analyzing their data.

Britain has reduced its own recommended interval from 12 weeks to eight weeks.

While the results of many studies take months to reach the public, explained Grunau, governments and public health officials have been given “stealthy spikes” during the pandemic to enable them to make sound policy decisions.

The research even allowed NACI to stray from mRNA manufacturers’ recommendations to wait 17-28 days between doses, to the recommended 56 days.

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“It’s a really interesting place,” said Grunau, who is also a scientist at the Center for Health Evaluation and Outcome Sciences.

“At no point in my career has funding and research, and the translation of new research findings into medical policy and practice been so rapid. “

Since the start of the pandemic, the COVID-19 Immunity Working Group has supported more than 100 studies across Canada.

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