We know that the COVID-19 mRNA vaccines (Pfizer and Moderna) can give 90 to 95% immunity within a few weeks of having both shots. But how well do they protect after only one shot? Do we really need a second shot? And how long is it safe to delay it? Lastly, what can we expect to be able to do differently while we wait for our second injection (about 3 months for most Canadians).
Here in Canada, our government decided to delay the second COVID-19 injection, to allow more people to get their first shot while supply is limited. It seems to me that this is a smart decision, even though it’s not what is recommended by the manufacturer. But the government has based its decision on emerging science and, like so many aspects of this new pandemic, we’re learning as we go and adjusting what we do as the science emerges.
How well do our bodies respond after the 1st shot?
Creating immunity is a process. You can think of it as your immune system learning something new. Just like in school, lessons are presented to you, then you have to study for a while to actually learn the material. With vaccines, the shot is the “lesson” and then your immune system has to get to work and learn what it has to do to protect you from the virus. This can take several weeks, and during this time, your immunity will gradually rise.
I found results of testing with the Pfizer vaccine and, since the Moderna vaccine works in the same way, results could be expected to be similar. Here are some numbers for how much protection was found after one shot:
· 70% protection against getting COVID-19, 3 weeks after the 1st shot
· 90% protection against hospitalization, 4 to 5 weeks after the 1st shot
Do we really need a 2nd shot?
While some may think that the first injection must give you half immunity and the second tops it up to the 85 to 95% we’ve heard about in the studies, it’s not quite like that. As you can see from the numbers above, at 4 weeks and longer, experts say you are probably still increasing immunity from the first shot.
But remember when you were in school, how reviewing the material would help you remember it much longer? With vaccines, the second shot picks up from the first, giving your immune system some extra training so it will remember how to fight the virus longer… In other words, your immunity will last longer if you get the second shot. So, yes, you do need the 2nd shot to keep the effect lasting longer.
How long does the first shot last?
Since the vaccine is so new, scientists still don’t know how long our immune systems will be able to recognize and fight off the coronavirus, even after the 2 injections. They suspect we may need a yearly booster. Remember “cramming” to refresh the knowledge stored away earlier so you could recall it more quickly during an exam?. Similarly, getting a yearly booster just before the virus season starts, as we do for the flu, can help our immune systems recognize the coronavirus more readily when risk of infection increases, as we stay inside more during the cooler weather in the fall and winter. Scientists will continue to measure how long immunity lasts and future immunization schedules will be based on what they learn.
This is the third coronavirus we’ve had to deal with in the past few years… SARS (aka SARSCoV1 or Severe Acute Respiratory Syndrome), MERS (Middle East Respiratory Syndrome that fortunately didn’t reach North America) and now SARS-CoV2 that causes COVID-19.
Scientists warn us that, the longer this virus circulates in humans anywhere in the world, the greater the risk it will mutate into an infection that can evade current vaccines. I was happy to hear that patents may be suspended on the current vaccines, opening up production to any company with an appropriate facility. We need to get vaccines to every country in the world for their protection now and for our protection in the future. The more the virus spreads anywhere in the world, the greater the risk of variants and new strains that can cause another wave.
Happily, I’ve read that researchers are also working on a vaccine that will work against all coronaviruses. If they are successful, we could expect that it might give at least some protection against the next SARS-CoV virus that comes along as well as the current one.
What can we expect to be different after the first shot?
Prime Minister Trudeau told us this week our communities should be able to open up somewhat, once 75% of the population has received their first shot. However, our top doctors warn that we will still need to continue some level of restrictions (although likely not quite as strict) to prevent a 4th wave… something none of us wants. It's looking like we won't be going to big music concerts this summer but the border to NS should be able to open up, allowing us to visit our kids. We love the "Atlantic bubble" we have when all provinces have low case counts!
But it all depends on making sure every case is tracked to its source, and everyone exposed is isolated to stop the spread. No exceptions. The variants are so contagious, it only takes one person doing a few errands or attending a gathering to start an outbreak.
And once you’re fully vaccinated?
Studies are ongoing to ensure fully vaccinated people cannot transmit the virus to others, even if they don’t get sick themselves. There’s also the problem with variants: will the existing vaccines protect us from these viruses that are slightly changed? Unfortunately, new variants continue to be found as the virus spreads around the world, and each will need to be tested and verified to be susceptible to the vaccine. I read this week about a triple-mutated variant that’s been discovered in India, dubbed the Bengal Strain. More changes in the virus increase the chance that it can evade the vaccines.
Supplies of vaccine are increasing quickly here in Canada, and our injection rate may soon be limited by the number of people who are trained to administer injections. At this point, that sounds like a good problem to have! Pharmacy technicians are being trained in some provinces to increase the capacity of pharmacies to immunize—a great idea, in my opinion. And many nurses and doctors have come out of retirement already to staff many of the government-run vaccine clinics.
Until significant numbers of people everywhere are vaccinated, the coronavirus will continue to circulate and mutate. I was glad to hear talk of suspending patents on vaccines so many more manufacturing plants can be more easily set up, greatly increasing world supply.
The future…
Once this virus has been brought under control around the world, the work needs to begin to build better global systems to monitor for new viruses, share information and develop systems to control contagious diseases. If not, we could be facing another pandemic all too soon.
As for me, I’m thinking that a mask or two will become a regular part of my travel gear, especially when flying. And it might just be a good idea to keep one handy during flu season too. It’s amazing that we didn't have enough cases of the flu this year to declare that flu season had started! I think I’ve gotten over the discomfort of wearing a mask in public and will keep using one both to protect myself when it seems necessary and to protect others when I have a cold… how about you?
References:
Why your 1st COVID-19 shot is more protective than you might think—CBC News Second Opinion
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