Residents >> COVID-19

Dr. Hirji Answers Vaccine Questions

Dr. Hirji Answers Frequently Asked COVID-19 Vaccine Questions

Dr. Hirji recently answered questions that may be holding back some younger people from getting vaccinated.

Vaccine and fertility

There’s no evidence of any fertility issues after the COVID-19 vaccination. Moreover, in our entire history of vaccine development, we’ve never seen a vaccine that harms fertility. This is a rumour that has no basis or evidence behind it.

Some people who voice this concern speak of “fertility research” around this vaccine. No such research however exists. This is all driven by rumours on the internet.

Unfortunately, during the third wave we just experienced, people who were pregnant were at high risk of being hospitalized with COVID-19. If anything, those planning to become pregnant soon are at greater need to be vaccinated than others.

Long-term Safety of mRNA Vaccines

This concern stems from there not being any studies yet showing long-term safety. Of course, a study can’t show long-term safety until we have lived through the long-term and observed what happens.

However, we know from the science and history of vaccines, that long-term effects don’t make much sense. Ultimately, all vaccines are introducing proteins from a dangerous pathogen to the body’s immune system so that the body can learn to identify and fight those pathogens off. Within a couple of weeks, no traces of the vaccine are left in the body as the immune system would have destroyed any proteins, and other elements of the pathogen introduced to the body will have degraded.

While mRNA vaccines like Moderna and Pfizer-BioNTech are new technologies for creating vaccines, these technologies represent only a small tweak from past vaccine technologies. mRNA vaccines, rather than directly injecting viral protein, injects the instructions to create viral protein. Those proteins are destroyed by the immune system, just like the proteins formed by any other vaccine. The mRNA degrades after a few days, and our body doesn’t have the ability to produce more of this foreign mRNA, so there’s nothing left of the virus long term. The only long-term impact of the vaccine is immune memory against COVID-19.

Safety issues do arise with vaccines, albeit rarely, in the short term, correlating with when vaccines stimulate the immune system. But we have no science or evidence supporting long-term impacts, and a track record of side-effects only arising in the short term in every other vaccine ever developed.

Vaccine and shedding

Shedding is the idea that when you are infected with a pathogen, you release that pathogen out into the world (e.g., you might cough out a cold virus). This is what enables an infection to spread to others. To shed a pathogen, though, you need to be infected.

Most vaccines are not giving you an infection, and so you do not shed the virus when vaccinated. This includes the COVID-19 vaccine. You’re injected with mRNA, instructions to make one particular protein of the virus, but not the full virus, so no virus is injected into you. Therefore, you can’t get infected from the vaccine, and you can’t “shed” the virus and infect others because of the vaccine.

Relaxing of Precautions with Two Doses

Many are wondering what we will be able to do once fully vaccinated. E.g., could we stop keeping distance, or stop wearing masks, or be able to enter crowded public places?

While in some parts of the world, governments are allowing fully vaccinated people to let down their guard down somewhat, this has not yet happened in Canada. Fully vaccinated people must continue to practice all the same preventive measures of unvaccinated and partly vaccinated people.

This is probably because in Canada, we have only started to offer second doses to most people. So until recently, almost no one had two doses of vaccine. With second doses now increasing, we can probably expect some guidance from our governments around this.

Mixing and Matching Vaccines 

With many vaccines, there are multiple companies producing a very similar vaccine. Think multiple companies producing bottled water. They have different labels but are essentially the same product. When this happens with vaccines, it allows us to mix-and-match vaccine products if we need multiple doses of a vaccine.

With COVID-19 vaccines, we see this with Moderna and Pfizer-BioNTech. Both vaccines are built on the same mRNA technology and are almost exactly the same. They are therefore interchangeable—you can get a first dose with one, a second dose with the other, and it’s equivalent to getting two doses of the same product. The two vaccines are so similar, you might as well be getting the same.

Where this gets more interesting is that early data shows that if one gets Pfizer-BioNTech after an AstraZeneca first dose, one may actually get better immunity than two doses of AstraZeneca. These two vaccines are designed using different technology, and so they aren’t equivalents. But it seems when getting an mRNA vaccine after AstraZeneca, each dose primes the immune system in a different way making the combination better than just purely getting AstraZeneca.

Going forward, as we try and vaccinate as many people as possible it is likely many people will get a mix-and-match vaccine series, depending on which vaccine product has recently been shipped to Canada.