COVID-19: New Study Says Quebec Made the Right Decision to Extend Intervals Between Vaccine Doses – Montreal | The Canadian News

COVID-19 vaccines are most effective when the second dose is given after a longer interval than recommended by vaccine manufacturers, according to a new study published Wednesday by the Quebec Institute of Public Health.

Due to a lack of supply, Quebec decided early in its vaccination campaign to administer a second dose of the COVID-19 vaccine 16 weeks after the first, instead of the 21 or 28 days recommended by vaccine companies.

The new study by the Institut national de santé publique du Québec says that “efficacy against infections increases when the interval between doses is greater than that recommended by manufacturers.”

For example, the study revealed that the Oxford-AstraZeneca vaccine was 47 percent effective in preventing infection when the second dose was given three to four weeks after the first, as recommended by the manufacturer. But that efficacy jumped to 92 percent when the second dose was given at least 16 weeks after the first.

2:32Quebec to administer the third dose of the vaccine to the elderly in long-term care homes

The study also found that three vaccines, Pfizer-BioNTech, Moderna, and AstraZeneca, have been highly effective in preventing COVID-19-related deaths.

“Among the 181 people who died from COVID-19 during the study period, only three had received two doses of the vaccine, resulting in a vaccine effectiveness against killing more than 97 percent,” according to the study, which was conducted between March 14 and September 11.

The researchers also found that all three vaccines were more than 92 percent effective in preventing hospitalizations, and the effectiveness of each vaccine did not change against various mutations of the new coronavirus, including the Delta variant.

On Tuesday, the institute released a projection that new infections and daily hospitalizations in Quebec should stabilize and begin to decline in December, if contacts between people remain the same. However, he warned that cases and hospitalizations could start to rise again if social contacts return to pre-pandemic levels.

Meanwhile, Quebec on Wednesday reported 594 new cases of COVID-19 and seven more deaths attributed to the new coronavirus. The Health Department said hospitalizations fell by 15 to 306, and 91 people were in intensive care, a decrease of three.