Does your COVID-19 booster shot seem like a long time ago? You’re not alone.
COVID-19 cases have been on the rise overseas and appear to be increasing in Canada, raising questions about when the population will need a second booster—and how effective it will be.
We spoke with Dr. Horacio Bach (he/him), clinical assistant professor in UBC’s division of infectious diseases, about vaccinating against the latest variants of SARS-CoV-2.
Most Canadians have had one COVID-19 booster shot. How long does immunity last after that first booster?
Four months after your last dose, the level of your protective antibodies is going down. And with the new Omicron variants, BA.4 and BA.5, it looks like it is even much shorter, because these variants have mutations that allow them to escape the immune system. The virus has already evolved a lot. Mutants can pop up anywhere, anytime. It’s not something you can control.
Will my immunity be stronger if I’ve also had a COVID-19 infection?
You naturally generate new antibodies with an infection, but we know that they will fade eventually. So an infection will give you extra protection, but it’s not going to be for one year.
How effective are the existing vaccines against new Omicron variants?
In Israel they started the fourth dose in January, so now researchers have started to evaluate. They’ve found out that the fourth dose is not as effective anymore. However, for immunocompromised people, or people with diabetes or another chronic disease that makes their immune system vulnerable, a fourth dose can still prevent COVID-19 from progressing to a severe case.
Does that mean we need a new vaccine?
We are using an old vaccine. The FDA (U.S. Food and Drug Administration) is now evaluating studies done by Pfizer that used the sequence of Omicron rather than the sequence of the original strain, which we are still using. So we may get an updated vaccine based on Omicron.
How long do you think that will take?
It’s actually very easy to do. All these vaccines are made by putting in the sequence for the RNA, so they just change the sequence. The point is that it has to be approved. I know Pfizer has presented some data to the FDA and is in negotiations for approval. They haven’t said when, but I imagine it will be a very short time. It will start in the U.S., and then they will provide it to other countries.
How urgent is this, given current trends in case numbers?
We don’t know at this point how prevalent BA.4 and BA.5 are here because we aren’t doing much testing, but these two variants are causing a big spike in cases in Europe.
The problem is that right now, COVID-19 is not considered as big a deal as it used to be. We aren’t using masks. The vaccine passport is not required anymore. Most people who get infected are OK after a couple of weeks. But we don’t know about BA.4 and BA.5. In other places like Europe and Israel, they are starting to see more severe cases in the hospital.
We are still in the summertime and people are going more outdoors, but that will be problematic when it starts to be cold outside and we’ve got indoor events.
Interview language(s): English, Spanish