Now that the Pfizer COVID vaccine has been approved in Canada, I have been able to access more data. Here are a few key points:
The vaccine comes in a multi-dose vial which contains 5 doses. Each dose of the vaccine is 0.3mL, which is less than most vaccines, which are usually either 0.5mL or 1.0mL The vaccine is given in the deltoid muscle in the upper arm, same as a flu
vaccine.
Doses are to be given 21 days apart. The Pfizer vaccine is the only one approved at this time, but if another vaccine becomes available, you cannot get a different vaccine for the second dose. You need to stick with the one you started with.
For non-medicinal ingredients, there is no thimerosal, formaldehyde, aluminum, or any preservatives. The safety of these ingredients in vaccines have been established, but I know that their presence does concern some people, so that’s why I mentioned it.
The vaccine has only been approved for 16 years and older. Some studies have been done in those as young as 12, but for the moment, the approval age is 16. As more data becomes available, I would expect that could change.
The frozen vials are delivered and kept in a special shipping container. When doses are needed, they are removed from the container and thawed in the fridge or at room temperature. It takes about 30 minutes to thaw at room temperature.
After thawing, sterile saline for injection is added to the vial. Once mixed, the vial of 5 doses must be used within 6 hours. It can be stored for those 6 hours in the fridge or at room temperature.
If thawed, the vaccine cannot be refrozen. The thawed but unmixed vials can be kept in the fridge for 5 days.
Preliminary effectiveness and side effects data have been released. The primary study listed had 36,621 participants. They were divided into two groups: 18,242 received two doses of the vaccine, and 18,379 received two doses of the placebo, both 21 days apart.
Average age in the study was 50.6 years old. Only 88 participants (46 vaccine, 42 placebo) were between 12-15 years old, and their data was not included in the effectiveness data in this study. Participants by nation: USA 28,253, Argentina 5100, Brazil 2455, South Africa 566, Germany 247.
Effectiveness was measured seven days after the second dose. It’s reasonable to think that you may have some immunity several days after one dose, but that information was not looked for in the study. Of the 36,621 participants, 170 cases of COVID-19 were confirmed. Of the 170 cases, 162 were from the placebo group and 8 were from the vaccine group. This puts the effectiveness level at approximately 95%
As far as side effects, the most common are injection site pain, fatigue, headache, muscle pain, chills, joint pain, and fever. These effects seem to resolve within a few days.
Local reactions such as pain at the injection site were most common, which averaged around 80%. About 1% of patients defined the pain as severe, meaning it prevented daily activity.
As far as systemic side effects, the data shows that in general, they were more common after the second dose. For example, in a study for ages 18-55, fever was noted in 3.7% (vs 0.9% with placebo) after Dose 1. But after Dose 2, that number roses to 15.8% (vs 0.5% with placebo).
Side effect studies were separated by age. One study did 18-55 and another did 56 and older. Interestingly enough, the 56 plus age group experienced a lower incidence of side effects in each major category. Going back to fever, in the 56 plus age group the incidence was 1.4% (vs 0.4% with placebo) after Dose 1 while 10.9% (vs 0.2% with placebo) after Dose 2. The pattern of increased likelihood of side effects after the second dose remained the same.
These participants will continue to be followed for 24 months to monitor effectiveness and any other reactions.
Based on the information provided, there is a lot of reason for optimism. Effectiveness looks good, and the side effects are pretty manageable. Duration of effect will not be known for a while yet as the passage of time will provide the answer. Supply and distribution will be a bit tricky but can be made to work. One advantage of a limited supply to start is that any process concerns can be worked out before scaling up.