Health & Wellness

What You Need to Know About Vaccines

By Judith Mewhort on May, 11 2021
6 minute read

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What was once a sliver of hope far on the horizon, the opportunity to receive a COVID-19 vaccine is rapidly approaching (some of you may have already received your first dose). Unsurprisingly, as the chance to receive the first jab increases, so have people’s questions about them. How do you get a vaccine? How effective are the vaccines? Are they resistant against the new variant? And other related questions.

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In this blog, we’ll walk through each type of vaccine, their effectiveness against covid and its variants, and cover any health concerns. Because each vaccine is different, we’ve broken down these questions by the individual vaccine. 

 

A brief note on vaccine effectiveness

When it comes to the effectiveness of vaccines, there are multiple ways to look at it. The first, and the one most commonly used in the media is the vaccine’s efficacy. Simply put the efficacy of a vaccine shows how well a particular vaccine performs at preventing individuals from getting the virus. 

A vaccine with only 50% efficacy may not sound like a good vaccine. However, that’s where it’s important to look at other measurements of vaccine effectiveness. For instance, a vaccine can have a low efficacy but protect against severe cases of covid that lead to hospitalization.  

Throughout this blog, when discussing the effectiveness of vaccines, we’ll be looking at both vaccine efficacy and effectiveness against severe cases. To learn more, check out this video.  

 

 

The Different Types of Vaccines

RNA or mRNA Vaccines

Vaccines include: Pfizer-BioNTech, Moderna

How do they work?

mRNA vaccines use a new type of vaccination technology. With regards to COVID, they provide the body with the blueprint needed to make the spike protein found within the virus. By making the spike protein itself, the body produces the antibodies required to fight the actual virus should it get into the system. 

Adenoviral vector vaccines

Vaccines Include: Oxford/AstraZeneca

How do they work?

Viral vector vaccines take advantage of a modified version of another virus to prime the immune system to defend against the target one. In the case of covid, the vaccine uses the common cold virus to provide the body with the needed information to create the spike protein found in covid-19.

 

How Effective are Vaccines?

Pfizer

Current research suggests that people who receive two doses of the Pfizer vaccine have 94% protection against covid. This protection occurs 7 days after receiving the second dose. 

There have also been “real-word” studies conducted on the effectiveness of the vaccine (ie. people who have been vaccinated as part of the general population have been monitored and followed-up with at various intervals). This research shows that Pfizer’s efficacy against symptomatic infection is 85% fourteen days after receiving the first dose.

According to the Centers for Disease Control and Prevention, clinical studies suggest that a single dose of Pfizer is 64% effective against hospitalization in patients older than 65. This number rises to 94% after they receive their second dose. In another small trial, Pfizer found that the vaccine is 100% effective in adolescents between the age of 12-15 years old. 

Studies have shown that the vaccine maintains its high efficacy for at least six months after the second dose. Importantly, the studies also suggest that vaccines have 100% efficacy against severe disease.

Moderna

In clinical trials, Moderna’s efficacy has shown to be 94% against symptomatic infection (this occurs 14-days after receiving the second dose). In the study, nobody who received the vaccine experienced severe symptoms

Just as the CDC collected observational data for Pfizer, they did the same for Moderna. In their observational data they found Moderna to be 80% effective against asymptomatic and symptomatic infection two weeks after receiving one dose and 90% effective two weeks after the second. Also similar to Pfizer, the vaccine’s efficacy appears to sustain for at least six months. 

AstraZeneca

Early data from February suggested vaccine efficacy to be 76% after a one dose, increasing to 82% once a second dose was received three months later. This early data has been supported by further studies. According to trials in the US, two doses of the AstraZeneca vaccine was shown to have 79% efficacy against symptomatic cases of Covid. The trials also found the vaccine to be 100% effective against stopping severe disease and hospitalization. 

 

Are Vaccines Effective Against Variants?

Pfizer

Yes. However, since most variants are new, it takes time to gather solid data on vaccine effectiveness against any particular one. Below is what is currently known about the prominent variants of concern in Canada.

  • UK variant (B.1.1.7): Appears to offer similar protection as in non-B1.1.7 cases. 
  • South African variant (B.1.351): Appears to offer a reduction in antibodies. This means that  there may be more cases of symptomatic Covid, but remain highly effective against severe cases and hospitalization.
  • Brazilian variant (P1): Current data suggests that the vaccine offers similar protection.   

Moderna

Yes. However, since most variants are new, it takes time to gather solid data on vaccine effectiveness against any particular one. Below is what is currently known about the prominent variants of concern in Canada.

  • UK variant (B.1.1.7): Appears to offer similar protection as in non-B1.1.7 cases. 
  • South African variant (B.1.351): Appears to offer a reduction in antibodies. There may be more cases of symptomatic Covid, however the vaccine remains highly effective in preventing severe cases and hospitalization.
  • Brazilian variant (P1): Appears to offer a reduction in antibodies. There may be more cases of symptomatic Covid, however the vaccine remains highly effective in preventing severe cases and hospitalization.

Though the vaccine efficacy may be reduced against specific variants, the Moderna vaccine appears to still maintain it’s high effectiveness against severe outcomes and hospitalization. 

 

AstraZeneca

AstraZeneca seems to have mixed effectiveness against variants. However, since most variants are new, it takes time to gather solid data on vaccine effectiveness against any particular one. Below is what is currently known about the prominent variants of concern in Canada and how they interact with AstraZeneca

  • UK variant (B.1.1.7): Though the antibodies generated by the vaccine were lower against the UK strain, the vaccine’s efficacy against symptomatic cases of the UK variant appeared to be similar to non-B1.1.7 cases. 
  • South African variant (B.1.351): There has only been one published study about this variant. The researchers found AstraZeneca has 10% efficacy against symptomatic cases. Throughout the study, they observed no cases of severe cases or hospitalization.  
  • Brazilian variant (P1): One small study found lowered antibody generation but similar protection against symptomatic cases as of P1 variant as in non-P1 cases.

 

Are there any safety concerns?

Pfizer and Moderna

Current research finds no safety concerns for either mRNA vaccine. It is not uncommon for people to feel unwell after receiving the first and second doses. Common symptoms include headache, chills, mild fever, and lethargy. If these symptoms persist for more than a few days, seek medical help. Full information on the safety of mRNA vaccines can be found on the UK Government website

AstraZeneca

Initially, there was some concern around blood clots in those who received the AstraZeneca vaccine. After a series of long investigations conducted by health authorities around the world, there is believed to be a link between these very rare blood clots and receiving the vaccine. 

While there is a risk, it is very small. Current estimates put it at 4 cases per million doses, which is a 0.0004% incidence rate.  In most age demographics, the risk of developing blood clots is much less than that of developing a severe case of covid. 

More commonly, people who receive the AstraZeneca vaccine may develop “flu-like” symptoms, including headaches, fever, and fatigue. If these symptoms last longer than four days, seek medical attention.

 

How to Register for a Vaccine

Each province has their own vaccine rollout strategy. When and where you can get vaccinated will depend on where you live. The Government of Canada website has a page that breaks down the vaccination process by province. Visit their page to learn more. 

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