On Dec. 11, as the Quebec City health region was preparing to administer the first Canadian doses of the COVID-19 vaccine, two residents at the CHSLD Saint-Antoine tested positive for coronavirus.
The next day, 15 more did. The people affected were from a single unit and were quickly isolated.
Officials had planned to inoculate the facility’s 230 or so residents partly to test whether the vaccine could inhibit the virus’s spread in an extended-care facility where it wasn’t already present. It now appears that by Dec. 14, the day the first shots were administered, it was too late.
More than 80 people at the centre, including 66 residents, have tested positive for the novel coronavirus since receiving the first of two vaccine doses.
The vaccine itself contains no viral or infectious material and the outbreak should not be taken as an indication that it is not effective, a health region official stressed.
A spokesperon for the CIUSSS de la Capitale Nationale said positive tests and resulting cases of COVID-19 were always likely. According to the evidence from clinical trials, it can take up to two weeks to achieve 50 per cent immunity, and a second dose is required after 21 days to reach 95 per cent.
“We expected there could be more cases among staff and residents who are vaccinated, because they’ve only had one dose of the vaccine,” Mélanie Otis said in an email.
According to the health region, 202 residents took the vaccine, along with 125 staff. It seems likely several of them were already infected with the coronavirus when they received the shot, Otis indicated.
In any case, immune responses aren’t typically instantaneous, Dr. Jacques Girard, the medical adviser to Quebec City’s chief public health officer, told Radio-Canada’s Première Heure.
“When we give someone a vaccine it’s to protect them,” but he cautioned that it often takes a couple of weeks to develop sufficient antibodies to stave off the virus, meaning that as of this week there should be signs the outbreak at CHSLD Saint-Antoine is starting to recede.
Residents and staff will begin receiving their second dose of the serum beginning Jan. 4.
Protection still key after vaccination
It wasn’t immediately clear how many of those who have tested positive for the coronavirus are symptomatic or have come down with COVID-19. As it stands, a total of 51 residents and 50 status are positive.
“The situation at CHSLD Saint-Antoine demonstrates the importance of protecting oneself even after vaccination. And even if the vaccine provided real protection after one dose … we know the virus can still transit through certain people,” Otis said.
The experience in Quebec City to this point lends credence to the belief previously expressed by some scientists that while vaccination is good at protecting people against getting desperately sick, it may not inhibit spread.
Another factor to consider, Otis said, is the clinical trials for the vaccine weren’t held in a long-term care environment that is dealing with an incipient outbreak.
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