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What Can I Do After My First Dose?

Clear COVID-vaccine guidance and real-world statistics to help you perform your own risk-benefit analysis

person receiving vaccine

The strategy to maximize first-dose distribution has created a strange situation—one that’s provoking lots of questions from Medcan clients:

  • “Can I see my grandkids now that I’ve received the first dose?”
  • “After my first dose do I still have to wear a mask?”
  • “Now that I’ve received my first shot can I still transmit COVID-19?”

Ultimately, all of these questions boil down to a single statement: How does getting your first vaccination change your life?

It’s an important dilemma because many people who have received their first shots are being given second-dose appointments in July or even later. That means that many of us will be spending the next few months in a half-vaccinated state. Which feels anticlimactic. We’ve passed the last year looking forward to the time when we can get vaccinated and when we do get that first dose, we wonder how excited to get.

The official guidance on the first dose says that it doesn’t actually change anything in terms of how you should behave. My colleague on Medcan’s Medical Advisory Services team puts it this way: “Internally, the first dose makes people feel less anxious about getting infected,” says Dr. Matthew Burnstein, “because they are more protected than they were before. But externally they shouldn’t change their behaviour at all.” This is because even fully vaccinated people can transmit the virus, although we think it is at a reduced rate.

Ultimately, how you behave after your first dose will depend on your own risk-benefit calculus. We triage risk against convenience and benefit every day. We face a small risk of death each time we go for a walk, and a slightly greater risk of death each time we take a ride in an automobile. And then there is the controversy about rare vaccine side effects. (See here and here for those rare risks quantified.) To provide you with the data required to make your own risk-benefit decision, here is some additional information about the first vaccine dose:

How much protection do I get from the first dose?

Real-world numbers suggest that all three of Canada’s most-distributed vaccines will eventually provide roughly similar protection after the first dose. (Note that the Johnson & Johnson vaccine, which has not yet been distributed much in Canada, provides full vaccination after only a single dose.) According to Public Health Ontario guidance based on real-world data from Israel, the U.K., the U.S. and Canada, vaccine effectiveness ranges between 60 to 80% two to four weeks after the first dose. To clarify, if you compare two groups of people—one that received the first dose with one that hadn’t—the first-dose group will have just 20 to 40% of symptomatic COVID infections, as defined by the presence of symptoms, compared to the first group.

The benefit is especially clear when considering risk of severe COVID, or death from COVID. Two to four weeks after the first dose, based on studies conducted on various populations around the world, the three vaccines range between 70 to close to 100% effective at preventing severe COVID. (Hospitalization numbers among those who received the first dose were near 0 to 30% of what they were for unvaccinated people.) Vaccine effectiveness is similar at preventing death. To clarify: Depending on the population studied, the number of people who died from COVID after getting the first dose ranged from near 0 to 30% compared to those who didn’t get any vaccine at all. For more specificity, this New England Journal of Medicine article based on people who received the Pfizer vaccine in Israel found that the first dose provided 74% effectiveness against hospitalization from COVID and 72% protection against death 14 to 20 days after the first dose.

Absolute numbers based on Ontario statistics represent another tool for people to gauge risk. According to Public Health Ontario figures, 3,493,866 people in the province received at least one dose of the vaccine between Dec. 14, 2020 and April 17, 2021. Only 0.06% of those 3.5 million individuals, or 2,223 people, became infected after receiving at least their first dose. And 66.9% of those post-vaccination cases experienced infections between 0 and 14 days after their vaccine. In other words, out of 3.5 million, only 736 people in Ontario have been infected with COVID more than 14 days after receiving at least one dose of the vaccine. That amounts to 0.02% of the people who have been vaccinated with at least one dose, or 2 in 10,000 people vaccinated. “The number of post-vaccination cases declines dramatically as time from vaccination increases,” says Public Health Ontario. And, “[a] marked decrease in post-vaccination cases is observed 28 or more days after dose 1.”

Source: The Economist

Can the first dose provide me with protection from the variants?

We are cautiously optimistic that the vaccines provide protection from the existing variants. However, the potential exists that the vaccines may not be as effective fighting future variants, raising the possibility that vaccines will need to be re-engineered (a process that can happen in as little as six weeks), and booster shots may be required. The reason that variants may require re-engineered vaccines is that existing vaccines work on SARS-CoV-2’s spike protein and mutations in that spike protein could create a variant that is too different for the vaccines to work against. For now, we have good data showing that existing vaccines protect against the B.1.1.7 strain (first identified in the U.K.), while efficacy may be lower against the B.1.351 variant (South Africa), the P.1 variant from Brazil and the B.1.617 variant from India. The B.1.526 variant first identified in New York appears to respond to the vaccine.

Can I still transmit COVID-19 after I’ve received the first dose?

The good news is that real-world data demonstrates that vaccination is reducing the spread of COVID-19 in populations with high-rates of vaccine uptake relative to populations where uptake is lower. However, we don’t yet know exactly how much risk of transmission persists after the first dose, or in people who are fully vaccinated. What is certain is that some risk of transmission does remain. After all, no vaccine on earth has ever been shown to be 100% effective, and we can’t identify transmission risk at the individual level.

Some will find these answers disappointing. In our imaginations we hoped that vaccines would bring about a binary transition: We were vaccinated, and the pandemic was over. Instead, after the third wave we face a slow thaw, an ongoing transition that likely will see us facing restrictions for months to come. What’s certain is that, because we are so connected globally, vaccines, mask wearing, testing and tracing will need to continue until every region of the globe has tamped down their COVID cases. We are only as safe as our highest COVID case-rate neighbours.

Things are better with the vaccine—and they will continue to get better as more people become fully vaccinated, which means both doses in the cases of the Pfizer, Moderna and AstraZeneca varieties. The U.S. Centers for Disease Control and Prevention (CDC) recently released guidance on what changes can be expected once that happens. The recommendations allow visiting indoors “with other fully vaccinated people of any age.” In addition, the CDC guidelines allow the fully vaccinated to visit “inside a home or private setting with one household of unvaccinated people who are not at risk of serious illness.” The guidelines also permit international travel without pre-travel tests or quarantining. Israel, where 95% of the population has received at least one dose, just experienced its first day without any COVID deaths, with new cases declining to the low hundreds.

Canada is behind both the U.S. and Israel in vaccine distribution. Even when we catch up, some small level of COVID risk will remain—as it does for the flu or even measles. The first dose offers a tremendous increase in our protection from COVID, and the second dose provides another 5 to 10% bump in effectiveness. As Canadians inch toward complete vaccination, we have much to look forward to, but along the way we must continue to play it safe and continue with mask use and distancing.

For additional guidance, see the primer put together by the Medical Advisory Services team, “Helping You Understand COVID-19 Vaccines.”

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