Moderna's COVID-19 vaccine lasting longer than Pfizer

“As I said many times, we don't yet have an absolute correlative protection (100 per cent protection), but Moderna seems to give higher antibody levels that stay longer,” says Dr. Bonnie Henry.

David Carrigg 3 minute read October 18, 2021

The COVID-19 vaccine produced by Moderna is proving to be longer lasting than its rival Pfizer vaccine and better suited as a booster shot for some people who are severely immunocompromised, according to B.C.’s provincial health officer Dr. Bonnie Henry.

Both vaccines are approved for use in Canada and widely used in B.C.

At a press conference last week, Henry said her office was increasingly getting information on which vaccines worked as well or better than others — based mostly on studies of COVID-19 antibodies remaining in people’s blood after vaccination.

This antibody response is crucial to how vaccines work, as this response is what fights off the disease.

“As I said many times, we don’t yet have an absolute correlative protection (100 per cent protection), but Moderna seems to give higher antibody levels that stay longer,” Henry said.

This was most likely because the Moderna mRNA vaccine has a higher amount of antigen (the substance that creates an immune response) than the Pfizer vaccine.

“It’s not surprising if we think about it. (Moderna has a) higher amount of the antigen — the mRNA in it — compared to Pfizer, and it seems to give a stronger response.”

So far, 83 per cent of British Columbians aged 12 and over are fully vaccinated — and the provincial government has begun its booster shot program, giving a third dose of vaccine to people in long-term care facilities and those who are moderately or severely immunocompromised.

Henry said booster doses will be either Moderna or Pfizer, but Moderna was proving to be the more effective option in some cases.

“The studies that were done with a third dose using Moderna gave a higher proportion of people who developed a strong immune response,” Henry said.

“So, we have been preferentially saying that people should use Moderna if you’re somebody who’s had a solid organ transplant. It gives the best possible chance of boosting that immune system and getting it up there.”

However, it is not clear whether Moderna has an advantage over Pfizer for people in long-term care.

The province began providing booster shots to seniors in long-term care facilities in early October and is now preparing to administer third doses to another 100,000 people, including those who are severely and moderately immunocompromised. People who are on dialysis or have severe kidney or renal disease will also be notified about when they can expect to receive their third shot.

Henry said information on booster shots for other people, including First Nations, over age 60 and health care workers who were vaccinated early, is expected to be provided by the end of the month.

Henry said there was more data becoming available showing that mixing and matching vaccines gives the body’s immune system several different ways of responding and it may give a stronger, longer lasting response.

The AstraZeneca and Johnson & Johnson vaccines are also approved by Health Canada but are not being used in B.C. at the moment.

— with files from Canadian Press