Everything you need to know about COVID-19 vaccinations
The invention of COVID-19 vaccines is a milestone in humanity’s journey of combating the COVID-19 pandemic. As more vaccines are being approved across the world, many people find it hard to keep up with the most recent medical information regarding different types of vaccines. We have summarized all you need to know about COVID-19 vaccines in this article.
How do vaccines work?
A vaccine contains a specific biological formulation that when introduced into a human body, will help the individual develop immunity against a particular virus or bacteria. In the context of vaccines against viruses, the biological formulation often contains a component of the harmful virus or a weakened version of the virus. Your body’s immune system will recognize and react to the virus or viral component by fighting them with antibodies. In the future, if you happen to come across the real virus, your immune system can recall how to fight the virus based on prior experience. This way, you are much less likely to contract the disease and suffer from any type of symptoms.
How will vaccines stop the spread of COVID-19?
An effective vaccine will protect you from developing COVID-19 when you come into contact with coronavirus. Even if you still catch COVID-19, the vaccine will greatly reduce the likelihood of serious illness, hospitalization, and death. Once the majority of the population is vaccinated, the coronavirus will not be able to infect many people, so herd immunity will develop. Herd immunity refers to a state where a significant portion of the population is immune to COVID-19 such that each person who acquires the infection passes it on to less than one person on average. Once this state has been achieved, only very few vulnerable people can be infected and transmit the disease. This breaks the chains of transmission and saves lives by directly protecting those vaccinated and indirectly protecting those who are unable to receive any type of vaccination due to medical contraindications.
What are the different types of COVID-19 vaccines available?
Currently, there are four COVID-19 vaccines available: Pfizer-BioNTech, Moderna, AstraZeneca and Janssen (Johnson & Johnson). These vaccines can be categorized based on their mechanisms of action.
mRNA vaccines include Pfizer-BioNTech and Moderna. This type of vaccine contains a nucleic acid code (mRNA) for the coronavirus spike protein. Spike proteins exist on the outer surface of the coronavirus. They help viruses attach to cells and cause disease. mRNA coding for spike proteins contains relevant information that can be read by human cells. When this special mRNA enters a muscle cell at the site of the injection, your cell can read its code and produce virus spike proteins. Your body’s immune system will identify these spike proteins as “foreign” and produce an immune response. This leads to the development of immunity against COVID-19.
Viral vector vaccines include AstraZeneca and Janssen: This type of vaccine contains a viral vector carrying the gene (double-stranded DNA) for coronavirus spike protein. The viral vector is a safe virus that does not cause disease but can deliver the spike protein gene into human cells. Similar to the mRNA vaccine discussed above, the spike protein gene enters a muscle cell at the site of vaccination, causing the cell to produce virus spike proteins. This will further trigger an immune response and eventually result in immunity against COVID-19.
It is important to realize that you cannot get COVID-19 from a vaccine. Current COVID-19 vaccines only contain biological materials that can stimulate an immune response in your body; none of them contain the coronavirus itself.
How effective are COVID-19 vaccines?
Pfizer and Moderna vaccines have the highest efficacies at 95% and 94.1% respectively. AstraZeneca and Janssen vaccines have lower efficacies at around 60 to 70%. Efficacy is usually measured by comparing how many vaccinated people contract COVID-19 with how many people in the placebo group contract COVID-19. In other words, efficacy represents the proportion of COVID-19 infections that could have been prevented by vaccination.
However, it is important to take note that different vaccination trials used different methods to measure efficacy. Directly comparing the efficacies of the four vaccines does not accurately reflect their potential for preventing disease. For example, Pfizer and Moderna vaccine trials tracked infections starting at least 7 to 14 days after the last vaccine dose in those who experienced symptoms. The Janssen vaccine trial set a higher bar by looking at clinical endpoints including the prevention of moderate to severe infection.
Another factor to consider when comparing efficacies of the four vaccines is the existence of variant viruses. Variants of the mainstream coronavirus emerged after the Pfizer and Moderna vaccine trials were completed. Therefore, it is likely that the efficacy of both vaccines may drop if those trials were replicated today.
Lastly, we have to take into account the fact that not all people who contract coronavirus will develop severe symptoms. Many people remain asymptomatic. Evidence suggests that all four vaccines protect against severe disease and hospitalization by almost 100%. This means that even if you do catch the coronavirus after receiving a vaccine, it is very likely you will not experience any symptoms. It is almost certain that you will not end up in a hospital or die because of the infection.
In conclusion, we should be cautious when comparing the efficacy of these vaccines. A lower percentage efficacy does not necessarily mean it is “a worse vaccine”.
Are COVID-19 vaccines safe?
As with all vaccines, there are risks of side effects. Based on trial data, side effects are common for all four vaccines, but they appear to be similar to other vaccines routinely recommended for older adults such as the Shingles vaccine. Common adverse reactions include muscle aches, pain and swelling at the injection site, fatigue, fever, headaches, swollen lymph nodes, chills, and diarrhea. Most symptoms trial participants experienced were mild to moderate and resolved in a couple of days. Severe reactions that required medical attention were very rare.
Based on current data, age seems to affect the severity of side effects. Older adults seem to experience fewer reactions that affect the whole body. Younger adults tend to experience more side effects, especially after the 2nd dose of Pfizer and Moderna. The reason may be that young adults produce greater immune responses to vaccines because they have stronger immune systems.
If you do experience side effects from the vaccine, you can take over-the-counter medications such as Tylenol or Advil. However, if you have other chronic medical conditions or take other prescription medications, you should make sure that Tylenol or Advil is safe for you before you take them. It is always a good idea to consult your local pharmacist before taking any non-prescription medications.
Are there any other differences among the COVID-19 vaccines?
The dosing schedule is different for the four vaccines: Pfizer, Moderna and AstraZeneca vaccines require 2 doses to achieve maximum protection. Janssen vaccine only requires 1 dose. It is common for vaccines to require more than 1 dose. The first dose primes the immune system so that it recognizes the virus, and the second dose boosts the immune response against the virus. You receive only partial protection after 1 dose but receive higher and more durable immunity after the 2nd dose.
In terms of spacing between the 1st and 2nd dose, it is critical to adhere to the minimum vaccine interval of 3 weeks. This is because if you receive 2 doses too close to each other, your body will not have sufficient time to produce an adequate immune response after the 1st dose. In this case, the efficacy of 2nd dose is uncertain. Due to limited vaccination supplies, you may be more concerned about receiving the 2nd dose too late. However, you can be assured that extending the interval between doses generally does not affect the efficacy of the vaccine. Currently, recommended intervals for the vaccines are only based on what was studied in trials. This does not mean that delaying your 2nd dose beyond what was studied will produce a suboptimal immune response. Further data suggests that it is acceptable to extend the interval between the 1st and 2nd dose up to 4 months.
Storage conditions are very different for different vaccines: Pfizer and Moderna vaccines must be stored in freezers while AstraZeneca and Janssen vaccines can be stored in industrial refrigerators. This makes a huge difference when it comes to accessibility and vaccination rollout. Extreme temperature storage requirements limit which facilities are able to distribute Pfizer and Moderna vaccines. Most clinics and pharmacies cannot afford large freezers and therefore can only offer AstraZeneca or Janssen vaccines.
If I receive the vaccine, do I still have to wear a mask?
It is essential to wear masks and practice social distancing even after you have received a COVID-19 vaccine. After all, no vaccine is 100% effective against the coronavirus. Also, while you may not get sick from the coronavirus after receiving a vaccine, you may still transmit the virus to other vulnerable people who are not vaccinated or unable to get vaccinated. As a result, continuing with precautions is still very important to limit the spread of the virus.
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