Vaccine decisions are based on data: Dr. Janice Fitzgerald
Public health boss says snippets of news and knowledge must be put in perspective
Few people knew much about which vaccines they were getting until the year 2020, when the fate of the entire globe seemed to hinge on a pharmaceutical solution for COVID-19.
Now, many can quote brand names, effectiveness, dose intervals and possible side-effects by heart.
Astrazeneca, for example, has an average efficacy rate of 67 per cent, making it seem undesirable compared to the shiny new line of MRNA vaccines by Moderna and Pfizer/ Biontech, which boast more about 95 per cent.
Skim through information from the U.S. Centres for disease control, however, and you’ll find this:
“Recent studies show that flu vaccination reduces the risk of flu illness by between 40 per cent and 60 per cent among the overall population during seasons when most circulating flu viruses are well-matched to the flu vaccine.”
In other words, that’s an average of 50 per cent in a good year.
The efficacy of a vaccine is not a hard number. Astrazeneca has been found to be 100 effective against preventing hospitalization or death, even if a person does contract the virus.
Side-effects are another issue.
Older vaccines have already gone through the wringer when it comes to sifting out possible complications, however rare.
Today, when adverse events after a COVID-19 vaccine are investigated, everyone knows about it.
The latest scare came from Israel, where officials said this week there are monitoring a small number of young people who developed heart inflammation after receiving the Pfizer vaccine.
But these are tens of people among millions who’ve received the shot. Even if a direct connection is established — as happened with Astrazeneca and a rare blood clot condition — the odds are extremely low and far outweighed by the benefits.
DOSE INTERVAL
A statement by Pfizer last month caused some alarm for those worried about the fact health officials in Canada have allowed an extension of the interval between doses of the vaccine from three weeks to 16.
The company said it stands by its original interval, based on its Phase 3 trials.
“There are no data from this study to demonstrate that protection after the first dose is sustained after 21 days,” it said in a statement.
That, says Newfoundland and Labrador’s chief medical officer of health, can sound alarming if people aren’t taking
external, real-world research into account.
“When Pfizer says that it doesn’t have evidence, it doesn’t mean there isn’t evidence,” Dr. Janice Fitzgerald said during Wednesday’s COVID-19 update. “It means Pfizer doesn’t have the evidence. It hasn’t done the studies to look at that.”
Fitzgerald says immunologists and other experts have been closely monitoring realtime data as the vaccines have rolled out.
“We know that at around two months, people have a good response to the first dose of the vaccine, and knowing what we know about vaccine science and the way that our bodies respond to vaccines, the chances of that protection dropping off rapidly in the next two months would be quite low,” she said.
PUT IN PERSPECTIVE
That explanation was echoed in a statement from B.C.’S Centre for Disease Control in March.
“For most vaccines, the first dose contributes the most towards short-term protection. Additional doses extend protection over the long-term and are often given months or even years apart.”
The centre noted that for most vaccines, antibody levels decline gradually over time and do not suddenly fall below protective levels.
“Even months or years later, another vaccine dose can boost antibodies to higher levels,” it said.
“Generally, vaccine manufacturing companies and national vaccine advisory bodies specify a minimum interval between vaccine doses but do not specify maximum intervals.”
Furthermore, the National Advisory Committee on Immunization (NACI) — from which provinces take their cues — spells out a key ethical consideration in a country where a third wave is on the rise and vaccines are not in abundance.
“Extending the interval between doses allows many more eligible people to be vaccinated earlier, which considerably enhances equity compared to leaving large groups of people unvaccinated until the summer.”