Early Findings in BC Show the First Vaccine Dose Reduced the Risk of Covid-19 by 80% or More

Early Findings in BC Show the First Vaccine Dose Reduced the Risk of Covid-19 by 80% or More

Posted on February 21, 2021 at 10:33 am by Bill Roberts
BC, Community, Provincial


Here are excerpts from a February 19  report from the BC Centre for Disease Control:

​”Early vaccine effectiveness results from British Columbia (B.C.) show the first dose of COVID-19 vaccine reduced the risk of COVID-19 in long term care residents and health care workers by 80 per cent within two to three weeks of receiving the vaccine.

“These findings, based on surveillance data, are very promising and reinforce the substantial benefit provided by the first dose of the mRNA COVID-19 vaccine in these priority populations,” said Dr. Danuta Skowronski, lead for the Influenza and Emerging Respiratory Pathogens Team at the BC Centre for Disease Control (BCCDC). “They also help to answer one of the important unanswered questions after the clinical trials about the effectiveness of the vaccines in the elderly and notably those within long term care.”

“The analysis, led by Dr. Skowronski, looked at COVID-19 cases that occurred among vaccinated long term care residents and health care workers between late December 2020 and early February 2021. Researchers observed a pronounced drop in the number of cases among vaccinated individuals in both groups, beginning about 14 days after vaccination, including a reduction in hospitalizations and deaths among vaccinated long term care residents.

“Vaccines begin to work a couple of weeks after vaccination. Researchers compared the risk of becoming a COVID-19 case in the first ten days following vaccination, before the vaccine would have had an effect, to the risk two weeks or more after vaccination.  In that way they were able to show vaccine effectiveness of 80 per cent or more beginning just a few weeks after vaccination. This means that a single dose of vaccine could prevent at least eight out of every 10 cases of COVID-19.

“The findings are encouraging as about 60 per cent of deaths in B.C. have occurred in residents of long-term care facilities. Since the COVID-19 vaccination program began, there has been a demonstrable decline in outbreaks and deaths in long-term care facilities…They are comparable to vaccine effectiveness results released by Quebec. Together, the studies reinforce the substantial protection for these important populations afforded by a single dose of COVID-19 vaccine.”

In a letter to the New England Journal of Medicine, Dr. Danuta M. Skowronski of the BCCDC reported even higher levels of protection in the general population, based on US data:

“Even before the second dose, BNT162b2 [the Pfizer–BioNTech vaccine] was highly efficacious, with a vaccine efficacy of 92.6%, a finding similar to the first-dose efficacy of 92.1% reported for the mRNA-1273 vaccine (Moderna).

“With such a highly protective first dose, the benefits derived from a scarce supply of vaccine could be maximized by deferring second doses until all priority group members are offered at least one dose. There may be uncertainty about the duration of protection with a single dose, but the administration of a second dose within 1 month after the first, as recommended, provides little added benefit in the short term, while high-risk persons who could have received a first dose with that vaccine supply are left completely unprotected. Given the current vaccine shortage, postponement of the second dose is a matter of national security that, if ignored, will certainly result in thousands of Covid-19–related hospitalizations and deaths this winter in the United States — hospitalizations and deaths that would have been prevented with a first dose of vaccine.