![]() ![]() All four seem to protect against more severe cases and hospitalization, but evidence is still limited. The vaccines appear to work equally well across subgroups defined by age, sex, race, ethnicity and among those at risk for developing severe COVID-19. 1,2,3,4 How well do these vaccines work in different populations? However, the National Advisory Committee on Immunization expects that short-term efficacy will likely remain high, even with an extended four-month interval between doses.įor AstraZeneca-Oxford vaccine data not shown for older adults >55 years due to a limited number of participants in this age group. We should be cautious in comparing these trials since they used different ways to measure efficacy, says Alison Thompson, associate professor at University of Toronto.Ĭomparisons should also take into account differences in the number and timing of doses. ![]() At least 136 cases of this variant had been detected in Canada as of March 8. In the Janssen trial, for example, efficacy was 74 per cent in the United States but dropped to 52 per cent in South Africa, where almost 95 per cent of cases were due to the B.1.351 variant. The lower efficacy in the AstraZeneca and Janssen trials may also be explained by a greater number of infections from variants of concern, which emerged after the Pfizer and Moderna trials were completed and against which vaccine protection is expected to be lower. “As we get more data about the kind of efficacy that they have over the longer term, we may see those (efficacy) numbers come down significantly for the mRNA (Pfizer and Moderna) vaccines,” says Thompson. ![]() However, the Janssen trial set a higher bar, looking to prevent moderate to severe or critical infection. The Pfizer and Moderna trials looked at prevention of any lab-confirmed infection starting at least seven to 14 days after the last vaccine dose in those who had symptoms. “I think the Johnson and Johnson (Janssen) one had much better clinical endpoints in the trials … there was a pretty low bar for establishing efficacy in the other trials,” she says. PCV13= pneumococcal conjugate vaccine RZV= recombinant zoster vaccine. However, we should be cautious in comparing these trials since they used different ways to measure efficacy, says Alison Thompson, an associate professor who studies public health policy and ethics at the University of Toronto. Older adults appear to have fewer reactions that affect the whole body, such as fevers, while enjoying similar or even higher protection than younger adults. In the AstraZeneca trial, in which the control group received a meningococcal vaccine rather than a placebo, a similar proportion of younger participants experienced reactions to the meningococcal vaccine and the COVID-19 vaccine. They appear to be much the same as some vaccines routinely recommended for older adults like the shingles vaccine, but worse than other vaccines like the high-dose flu shot. Put another way, it represents the proportion of COVID-19 infections that could be prevented by vaccination). (Efficacy measures how many vaccinated people contract COVID-19 compared with how many infections occur in the placebo or control group. Lower efficacy, in the 60 to 70 per cent range, was found for the AstraZeneca and Janssen products. The Pfizer and Moderna vaccines have the highest efficacy at around 95 per cent. How do the four vaccines compare in efficacy and safety? AstraZeneca and the University of Oxford’s vaccine as well as the first single-dose shot from Janssen, a unit of Johnson & Johnson, were recently authorized by Health Canada, joining the Pfizer-BioNTech and Moderna mRNA vaccines approved in December. ![]() There are now four vaccines available to Canadians. Update: As of May 10, the National Advisory Committee on Immunization (NACI) recommends that the AstraZeneca COVID-19 vaccine should not be used in adults under 30 years of age due to a rare but serious side effect of blood clotting.Īs more and more Canadians become eligible for vaccination in what has become a crowded landscape of COVID-19 vaccines, many may wonder what to expect when they roll up their sleeves. ![]()
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