Answering Some of the Most Commonly Asked Questions Around the Ongoing COVID-19 Vaccination
With vaccination campaigns currently ongoing worldwide, 312 million vaccine doses have been administered so far (as of March 9, 2021), with the U.S. being the country with the highest number of fully vaccinated people, that is of 31.49 million as shown in the chart below.
Being the first time that such a big scale vaccination process is being executed, combined with a never before seen interest from the public, there are a multitude of concerns and questions that we’re wondering about. In this blog post, I will be trying my best to answer some of the most frequent questions I came across recently:
- With the emergence of new virus variants, is vaccination still a viable option to combat the pandemic?
- Is it safe to delay the second vaccine dose for vaccines such as Pfizer-BioNTech vaccine?
- Why does the immunity gained from vaccination last longer than the one conferred after a natural infection?
- Should people previously infected with the COVID-19 also get vaccinated?
- Should people previously infected with the COVID-19 get both doses of a 2-dose vaccine?
1. With the emergence of new virus variants, is vaccination still a viable option to combat the pandemic?
Before answering this question, let’s first understand how new virus variants emerge.
Once the virus infects our body, it will multiply at a very high rate in order to increase its chances of survival. During these multiplications, errors might occur resulting in a slightly different version of the virus to be created. These errors in replication are called mutations, and the resulting slightly different virus is called a variant. As a result, variants of a given virus can either be weaker, stronger or similar to the original virus version. This characteristic is completely random due to the stochastic nature of the mutations. In the case where the variant is stronger than the original virus, it will eventually be able to propagate much more effectively, due to a stronger ability to bind to human cells for instance, and thus taking the lead as the more dominant version of the virus.
Given this brief explanation, can you spot at which stage can we interfere to stop the emergence of new variants? Well, it’s in the multiplication stage. Basically, when we don’t allow the virus to multiply within our body in the first place, no new mutations will occur, and consequently, no new variants will emerge. Hence the extremely important role of vaccines: when the virus infects a vaccinated person, the immune system will instantly fight the virus, leaving little to no window for virus’ multiplication. That’s the reason why vaccines are extremely effective, more specifically the rate of vaccination, as it will heavily decrease the playground in which replications occur, thus lowering the chances of an emergence of new, stronger, virus variants.
2. Is it safe to delay the second vaccine dose for vaccines such as Pfizer-BioNTech vaccine?
Globally, the rate of vaccination is proving to be slower than expected due to a multitude of factors, such as supply shortages or lack of funding. Some countries however have managed to vaccinate a huge proportion of their citizens, like Seychelles and the United Arab Emirates, whereas others are experiencing much slower vaccination rates. In the latter countries, governments are considering giving just one vaccine dose to as many people as possible, thus delaying the second vaccine dose. For instance, UK citizens who received their first vaccine dose will have to wait up to 3 months in order to get their second vaccine dose, which is in huge contrast with the FDA-recommended time frame of 3 weeks for Pfizer-BioNTech and 4 weeks for Moderna vaccines.
So, is it safe to push for that long the second vaccine doses? According to the senior vice president of Pfizer Vaccine Clinical Research and Development Dr William C. Gruber, the efficacy of the Pfizer-BioNTech vaccine is 52% after the first dose and it rises to 95% after the second dose. Based on such information, delaying the second vaccine dose will lead to having partially immune people for a shorter period of time, and this incomplete protection will in fact accelerate the emergence of new virus variants and here’s why: in research work, new virus variants are produced by exposing the original virus to a low quantity of neutralizing antibodies that will serve in crippling but not in killing the virus. Such an environment will lead to having the virus trying more rigorously to escape (i.e., survive), and this is accomplished by means of mutations, where the stronger variants would prevail in their fight against the antibodies. That’s why it’s tremendously important to follow the FDA recommended time frame between the two vaccine shots in order to avoid such major problems that can occur if we were to space out the period between both doses.
Recently, a study conducted on 9109 people was published in the Lancet medical journal trying to contradict the above numbers provided by the official Pfizer-BioNtech studies. This study showed that the Pfizer-BioNTech first dose is 85% effective against infection, with that effectiveness being attained anywhere between 2 to 4 weeks after getting the first shot. Nevertheless, this study suffers from a bunch of limitations, as it was bound to one hospital, with the choice of participants lacking heterogeneity, as they were all young and relatively healthy. In any case, if follow-up studies further back-up these numbers, giving just one vaccine dose to as many people as possible without worrying about when to give the second dose will be a much safer option (as it will eliminate the partially immune cases), however, while waiting for such studies, delaying the second vaccine shot should not be taken into consideration due to its high risk factor.
3. Why does the immunity gained from vaccination last longer than the one conferred after a natural infection?
When the virus itself infects our body, it will try its best to escape and reduce the efficacy of our immune response for it to be able to survive longer and multiply faster. For instance, the virus can reduce the interferon response which is a type of immune response developed against the virus. This will lead to a reduction in the overall efficacy of the immune response and a reduction in the efficacy of the generation of a memory response (which in a nutshell is the essence behind our long term protection against the virus. For a more detailed explanation please refer to my previous blog). On the other hand, vaccines present to the immune system an inactivated virus or a part of the virus (a purified spike protein in the case of Pfizer and Moderna vaccines) that are unable to aggressively fight and harm our immune system. Thus, there will be no other distractions that could mess with the efficacy of the immune response, leading to a much favorable matchup for our immune system and subsequently to a stronger generation of a memory response. On top of that, the vaccine contains adjuvants that are ingredients like aluminium hydroxide or aluminium phosphate which improve the immune response, by increasing the time in which the vaccine remain present at the injection site or by stimulating local immune cells. So, vaccines are produced with the intent to trigger a stronger and hopefully longer lasting protection than a natural infection. As for the duration for which a vaccine would protect us from this disease, it is still uncertain and studies are ongoing in order to answer this question.
4. Should people previously infected with the COVID-19 also get vaccinated?
As we explained in the previous paragraph, vaccine immunity is stronger and hopefully lasts longer than the natural infection. For that major reason, people previously infected should absolutely get vaccinated. That being said, and given that these people could be protected “for six months and possibly longer”, it is recommended to wait several months before prioritizing them to get the vaccine. This is simply due to the fact that even if their immunity is not as strong as a vaccine-provided immunity, other non-infected people have quite literally zero protection against the virus. It’s up to each country’s health authorities to specify how many months do these people have to wait in order to get their vaccine dose.
5. Should people previously infected with the COVID-19 get both doses of a 2-dose vaccine?
An early study conducted in the department of Microbiology at Icahn School of Medicine in Mount Sinai New York, showed that there is no need for a second vaccine shot for people previously infected, as data revealed that the immunity of people previously infected and getting a single vaccine dose “is equal or even exceeds” that of people who never caught the virus and received the two vaccine doses. However, provided the limited sample sizes in this study, more data is needed to solidify this claim. Based on that study, France was the first country that officially issued the recommendation of giving a single vaccine jab of a two-dose vaccine for previously infected people.
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