With almost 100,000 Canadians receiving at least one of the four approved vaccines each day, widespread immunity against the coronavirus is slowly becoming a reality. But, as more vaccinations are rolled out and life inches back to pre-pandemic times in some parts of the country, the question of how long that immunity will last after the final shot is on a lot of people's minds.
According to new research from Pfizer and Moderna, it looks like COVID-19 immunity will last at least six months in fully vaccinated people, though studies are ongoing. In a statement released by Pfizer-BioNTech on Thursday, immunity against the coronavirus is confirmed to last at least half a year for people who have been fully vaccinated with the Pfizer shot. The company, following an observation of 927 symptomatic cases during its phase 3 study, concluded that its vaccine remained 91.3% effective against the virus for up to six months after. Pfizer also confirmed that the COVID-19 vaccine was 100% effective against severe disease, as defined by the CDC; 95.3% effective against severe COVID-19 symptoms, as defined by the U.S. Food and Drug Administration (FDA); and 100% effective against the highly transmissible B.1.351 variant of the coronavirus.
The Moderna vaccine also appears to remain effective in fighting against COVID-19 for at least six months after the second shot, according to an April 6 report in The New England Journal of Medicine. The vaccine showed a 94% efficacy in the company's own phase 3 trial, in which 33 adults were tested. Moderna will continue to monitor the subjects' antibody levels in the coming months.
What will these findings mean for future booster shots and prolonging the vaccine’s effectiveness? Given the still very new nature of this data, medical experts just aren’t sure yet.
For the Moderna vaccine, scientists contributing to The New England Journal of Medicine reported that they are “determining the effect of a booster dose to extend the duration and breadth of activity against emerging viral variants.” Pfizer also appears to be determining the need for a booster shot; its Thursday press release includes mention of “a potential second booster dose of BNT162b2 [the Pfizer vaccine sequence] and/or a potential booster dose of a variation of BNT162b2 having a modified mRNA sequence.”
Experts will no doubt advise people who have been vaccinated to receive booster shots if and when they are developed. Until those shots become reality, those of us who have been partially or fully vaccinated can rest easy knowing that we remain between 80 to 90% protected against COVID-19 for the time being.