Hospital staff may have to wait for second shot

While first dose gives some coverage, expert says efficacy is ‘substantially lower’ than getting both

Some Hamilton health-care workers are likely to see their second dose of COVID vaccine delayed due to a looming nationwide shortage, one hospital network confirms.

If and how that might affect efficacy in the short-term remains unclear.

In an email to The Spectator on Thursday, Hamilton Health Sciences (HHS) said hospital health-care workers who received their first vaccine before Monday — when the province temporarily tightened rules on who can get a vaccine — will still be inoculated “as scheduled” in the coming days. But, the hospital network added, it is still waiting for direction from the province and “we are looking at potentially delaying second doses for most individuals.”

HHS did not say how long the delay might be.

The need to hold off on second doses stems from an abruptly announced decision from Pfizer last week; the pharmaceutical giant will temporarily pause shipping vaccines to Canada due to retooling at its Belgium plant.

In the meantime, supply will be running low.

The debate around delaying second doses is a contentious one. The Pfizer-BioNTech vaccine is meant to be administered in two doses, 21 days apart. Still, the first dose gives some coverage. And some countries, such as Israel, have long prioritized the first shot for citizens and delayed the second.

But the question remains: How long of a wait is too long?

Dr. Mark Loeb, infectious disease physician and professor at McMaster, says any delay is too long.

“My view is that two vaccine doses should be given on schedule and that this should be a priority to those at highest risk of complications,” Loeb told The Spec. “For health-care workers who have been receiving the Pfizer vaccine, the closer that the intended schedule can be followed, the better — second dose 21 days after the first dose.”

Loeb noted that the efficacy of just one dose is “substantially lower” than both.

Recent data shows one dose of Pfizer is about 52 per cent effective — with a second shot, it’s 95 per cent effective — but Loeb said unpublished data from Israel suggests the efficacy of just one dose is “even lower than reported in the clinical trial.”

Ashleigh Tuite, an epidemiologist and assistant professor at the University of Toronto, told the Toronto Star earlier this month that she understands the need to get shots out fast, but she has misgivings about “going off label.”

The Health Canada and the U.S. Food and Drug Administration approvals for Pfizer and Moderna are both based on a two-dose regimen, she noted.

Still, Ontario is now saying a 42-day delay is acceptable for the Pfizer vaccine — for some people.

In a Thursday statement, a spokesperson from Ontario’s Ministry of Health said people who live in long-term care and high-risk retirement homes, along with their essential caregivers, who received their first dose of the Pfizer vaccine will receive their second in 21 to 27 days.

Staff vaccinated at the same time as residents in the homes will follow the same schedule.

“All other recipients of the Pfizer-BioNTech vaccine must receive their second dose after 21 days and before 42 days,” the statement reads. “For individuals who received the Moderna vaccine, the dose schedule of 28 days will remain.”

The adjusted inoculation timeline aligns with recommendations from the National Advisory Committee on Immunization, the statement read.