I got Astrazeneca. Now what?
HERE’S WHAT CANADIANS NEED TO KNOW ABOUT THE COVID VACCINE
More than two million Canadians are likely wondering what’s next after several provinces — Alberta, Saskatchewan and Ontario — pushed the pause button on first doses of the Astrazeneca vaccine for COVID-19.
Alberta and Saskatchewan say it’s a matter of supply constraints; there simply isn’t enough Astrazeneca in the provinces. Ontario is pausing first doses out of an “abundance of caution” over the risk of VITT — vaccine-induced thrombotic thrombocytopenia — an unusual clotting disorder that can cause rare cases of serious blood clots, including clots in the brain and other critical organs. Ontario is also expecting increased supplies of Pfizer and Moderna, MRNA vaccines that haven’t been linked with VITT. The risk-benefit has shifted, experts say. Here’s a breakdown of where things stand with the Astrazeneca vaccine.
WHAT’S THE RISK OF VITT?
The risk seems to change based on the best estimate of the day. In early April, Health Canada put the risk as low as one case per 250,000 doses. By Apr. 28, the estimated rate of VITT in Canada was one case per 100,000 persons vaccinated with Astrazeneca or Covishield, the Astrazeneca vaccine made under licence in India.
Internationally, estimates vary by country, with published estimates ranging from as high as one case per 26,000 doses in Norway, to as low as one per 127,300 doses administered in Australia. “These rate estimates evolve as cases continue to be reported and investigated,” the Public Health Agency of Canada said in a statement to the National Post Tuesday.
Hours later, Ontario’s COVID-19 Science Advisory Table reported that the risk of VITT in Canada, as of May 8, stood at approximately one per 55,000, but that “several presumptive cases are still under investigation.” The VITT rate in Ontario breaks down to roughly one case per 60,000 doses.
Symptoms include a severe headache, blurry or double vision, difficulty speaking, shortness of breath, severe chest, back or abdominal pain and unusual bleeding or bruising.
There have been a dozen confirmed cases in Canada so far and three deaths.
HOW LONG AM I AT RISK?
To date, reported cases of VITT occurred between four and 28 days after receiving the Astrazeneca vaccine. The blood clots are associated with low platelets, blood cells that help form clots to stop bleeding. “These blood clots are different from the blood clots most people are familiar with; they are more aggressive and are more likely to cause death or severe disability, even with early diagnosis and treatment,” Ontario’s COVID science table wrote in a lay summary.
Nearly all cases of VITT have occurred after the first dose. Data from the U.K. suggests the risk of VITT after a second dose of Astrazeneca is roughly one in a million.
It’s not clear who is at higher risk of VITT, because the disorder is unique from other bleeding or clotting problems. “Currently we do not have any evidence that VITT is more common in people who have had blood clots before, people with a family history of blood clots, people on birth control or other hormones, people with autoimmune diseases, people with low platelets or other platelet disorders or pregnant people,” the science table said.
CAN I STILL GET A SECOND SHOT OF ASTRAZENECA?
Saskatchewan residents who received their first dose of Astrazeneca will likely be given Pfizer for their second dose because of supply shortages, Dr. Saqib Shahab, Saskatchewan’s chief medical health officer, said Tuesday. Should more shipments of AZ arrive, Shahab said people would likely be given the choice whether to receive Astrazeneca or Pfizer for their second shot.
In Alberta, all new first doses, with some exceptions, are being booked with the MRNA vaccines Pfizer and Moderna. The province’s remaining supply of Astrazeneca will be used for second doses only. Alberta hasn’t yet decided whether people who had one dose of Astrazeneca can get Moderna or Pfizer for their second shot.
Some 850,000 people in Ontario who have received a first dose of Astrazeneca are also waiting to hear whether they will be switched to a different vaccine for dose two, or have the option of sticking with Astrazeneca. Health officials are awaiting preliminary results, due Wednesday evening, of a trial led by University of Oxford researchers testing mixing two doses of different vaccines, Astrazeneca followed by Pfizer, or vice versa.
SHOULD I HAVE BUYER’S REMORSE?
Absolutely not.
“Based on the much higher risks of COVID-19 infection recently observed in Ontario including hospitalization, serious illness and death, we maintain that those who received their first dose with the Astrazeneca vaccine did absolutely the right thing to prevent illness, and to protect their families, loved ones and the communities,” Dr. David Williams, Ontario’s chief medical officer of health, said in a statement.
“Yes, we’ll have to figure out second doses, and potential mixing,” Mcmaster University infectious diseases specialist Dr. Zain Chagla said on social media. “But at the end of the day, no one is going to count the patients saved by taking vaccines, but only count the side effects. In the U.K. for example, an excess of 10,000 lives were saved with AZ.”
Ontario has roughly 50,000 unused doses of Astrazeneca, and is expecting 254,500 doses the week of May 17. The province is reviewing data and considering options for using the vaccine for second doses, saying Wednesday that guidance around second doses for those who have received a first will come “shortly.”