More than 100 Manitobans immunized with a single dose of the COVID-19 vaccine caught the coronavirus more than two weeks after receiving a shot, including six who died.
As of April 9, the province was aware of 111 post-immunization infections that occurred at least 14 days after a shot was given in people who had received only one of the required two doses of COVID-19 vaccine.
It takes about two weeks for the body to develop an immune response after receiving the vaccine, and each person will have varying levels of immunity, said Dr. Joss Reimer, medical lead for the provincial COVID-19 vaccine task force.
"Most people will be protected after dose one, but you don’t know if you’re one of those unlucky people who didn’t get that full immune response... Our goal is to lengthen how long the immune response stays strong, but there will be a small subset of people where that second dose is what triggers a good response," she said.
The 111 infections were reported among 192,131 people who had received a single vaccine dose. Of those 111, nine were hospitalized and six died.
Of the 67,716 people in Manitoba who had received two doses of the COVID-19 vaccine as of April 9, nine were diagnosed with the virus more than 14 days after their last shot.
None had been hospitalized or died.
"We were encouraged though that out of the hundreds of thousands of people who have received vaccines, that we still have only seen 111 cases of COVID showing up after the vaccine," Reimer said. "We actually are quite reassured that the vaccines are very effective."
In early March, following the recommendations of the National Advisory Committee on Immunization, the province decided to begin delaying required second doses up to four months in order to give more people the protection of a single dose.
According to vaccine manufacturers, first and second doses should be given 21 and 28 days apart for Pfizer-BioNTech and Moderna products, respectively.
Medical experts in charge of the vaccination rollout on First Nations communities have determined second doses of Moderna will be administered as close to 28 days as possible following a higher rate of post-immunization infection among First Nations people than expected after a single dose.
Each person’s body will have a different response to the vaccine, and while highly effective at preventing severe disease, they do not offer a 100 per cent guarantee, Reimer said.
"Once we have enough people in the community vaccinated, we start to protect each other, and so even for those folks who the vaccine didn’t protect them from the virus, if there’s no virus circulating, they’re still protected," she said.
The province also noted 162 people have been diagnosed with COVID-19 within the 14 days following their immunization. Twelve of those people were hospitalized, and four of them died.
In those cases, it is likely the infection occurred before immunization or shortly afterwards, before the body could build an immune response, Reimer said.
Of those who received a second dose, 24 were diagnosed with COVID-19 within 14 days after getting the second shot, and three people were admitted to hospital.
Danielle Da Silva
Danielle Da Silva is a general assignment reporter.