You Got the COVID-19 Vaccine - Now What?

Getting vaccinated

With the COVID-19 vaccine rollout underway and a renewed sense of hope stemming from an aggressive vaccine dispersal plan, a common question has begun to emerge.

What is the first thing you will do after you get the COVID-19 vaccine?

Some people dream of going to crowded concerts, theme parks or sports arenas. Others hope to see family members again; grandparents long to hold their grandchildren, extended family members hope to catch up at weddings and summer barbecues. Yet others, like healthcare workers, are simply grateful to be able to do their job a bit more safely.

But what is the reality of a post-vaccine life? How soon will life go back to ‘normal’?

In an ideal world, the COVID-19 vaccine would provide us with immediate and permanent immunity, and we would be free to socialize to our heart’s content. However, modern medicine has its limitations, and the COVID-19 vaccines are no exception.

How do the COVID-19 vaccines work?

mRNA Vaccines

The two COVID-19 vaccines approved in the U.S. (from Pfizer and Moderna) are messenger RNA (mRNA) vaccines. mRNA is normally used in our cells as a sort of instruction manual to create proteins.

The Pfizer and Moderna vaccines work by introducing a new mRNA instruction manual in our body to help our immune system build defenses against the SARS-CoV-2 virus (the virus responsible for the COVID-19 pandemic).

So how does mRNA help build an immune defense?

When a person encounters SARS-CoV-2, their body creates cells known as T-lymphocytes and B-lymphocytes that attack the virus. Once created, these T-lymphocytes and B-lymphocytes ‘remember’ how to fight the virus in the future.

COVID-19 mRNA vaccines work by tricking the body into creating T-lymphocytes and B-lymphocytes to fight SARS-CoV-2 without needing to be exposed to the virus first. The mRNA in the vaccines instructs cells to create a protein called the spike protein.

The spike protein is normally located on the outer surface of the SARS-CoV-2 virus and is not something that our cells would normally produce. When someone gets a COVID-19 mRNA vaccine, their cells begin to create the spike protein (which, by itself, is harmless).

In response, their body creates T-lymphocytes and B-lymphocytes that attack the spike protein. If the person is then exposed to SARS-CoV-2, the T-lymphocytes and B-lymphocytes can quickly attack the spike protein on the surface of the virus and neutralize it. The faster a person’s body can neutralize the virus, the less likely they are to get sick.

In most cases, it takes a few weeks after vaccination for someone’s body to produce T-lymphocytes and B-lymphocytes. For this reason, the Pfizer and Moderna COVID-19 vaccines (both of which require two doses) require a period of three to four weeks between the first and second doses. One way to think about the two doses is like building up an army. The first dose builds an initial army defense, while the second one improves upon the army in terms of both quality and quantity, giving the immune system a better chance to be able to fight off and neutralize the SARS-CoV-2 virus.

Adenovirus vectored vaccines

Although not yet approved for use in the U.S., another type of COVID-19 vaccine is on the horizon. The Oxford-AstraZeneca vaccine, which is approved for use in the U.K., uses a technology known as adenovirus vector technology. Adenovirus vectored vaccines and mRNA vaccines are similar in that they both help the immune system build up an army of T-lymphocytes and B-lymphocytes to fight SARS-CoV-2. However, the vaccines achieve that goal in slightly different ways.

When someone receives an mRNA vaccine, the mRNA goes into their body and their cells treat the foreign mRNA the same way that it would treat mRNA that is normally produced in their body (i.e., they create the protein that the mRNA instructs, and the mRNA is then degraded). In contrast, adenovirus vectored vaccines use a harmless virus known as an adenovirus to insert genetic material (DNA) into cells.

When someone gets the Oxford-AstraZeneca vaccine, the adenovirus enters their cells and the DNA is turned into mRNA. The mRNA then instructs the cells to make the SARS-CoV-2 spike protein and build an immune response in the same way as mRNA vaccines.

Adenovirus vectored vaccines have some benefits over mRNA vaccines. Chief among these benefits is their ability to be stored at warmer temperatures. Because mRNA is very fragile, mRNA vaccines need to be stored at extremely cold temperatures or else the mRNA will fall apart and the vaccine will become ineffective.

Adenoviruses, on the other hand, tend to be more stable at warmer temperatures, making them easier to store and transport. However, adenovirus vectored vaccines also take longer for scientists to create. There are hundreds of adenoviruses that exist naturally in the world and it can take time for scientists to determine the most appropriate adenovirus to use.

It is important for scientists to pick an adenovirus that is very different from adenoviruses that most people have encountered in their lives and given the fact that we all encounter adenoviruses throughout our lives (often without knowing it) identifying and testing them can be time consuming. If scientists were to choose an adenovirus that is too similar to ones that we’ve encountered before, our immune system would swiftly eliminate the adenovirus, rendering the vaccine ineffective.


Can I infect other people after I get the COVID-19 vaccine?

Most vaccines that fight against viral infections also reduce virus transmission. However, because the COVID-19 vaccines do not completely stop SARS-CoV-2 from entering the body and replicating, it is still possible for people who have been vaccinated to infect others.

Unfortunately, we don’t yet have a definitive answer regarding how well the COVID-19 vaccines reduce transmission - but scientists are working on it.

In the early stages of the COVID-19 pandemic, scientists’ primary goal was to develop a vaccine that could prevent severe infection. Fortunately, the vaccines are exceptionally good at doing so; very few people who are vaccinated end up in the ICU or on a respirator. Now that the initial clinical trials are complete, scientists have begun to investigate secondary questions, like whether the vaccines can reduce or prevent transmission of the virus. However, because vaccine trials examining transmission are still ongoing, we don’t yet have an answer.

“We don't know if the vaccines will reduce transmission, but it’s possible that they will,” Adan Becerra, an epidemiologist and assistant professor at Rush Medical College told BioSpace. “I'm hopeful, and there are a lot of people in the vaccine world who are hopeful. We do know that it's possible to develop an effective vaccine for a disease outcome that doesn’t completely prevent transmission. On the other hand, there are vaccines that are fully efficacious, like the polio vaccine, that also prevent transmission. And so, because these are new mRNA vaccines, it could really go both ways. We don’t know for sure yet.”

A preprint released by Oxford University this month suggests that the vaccines may indeed reduce transmission. The preprint, which outlines preliminary data from Oxford-AstraZeneca vaccine trials, reports a 67% reduction in transmission rate among people who received one dose of the Oxford-AstraZeneca vaccine.

While these preliminary data are promising, it is important to note that the trials are not yet complete, and we won’t have a definitive answer to how well the Oxford-AstraZeneca vaccine reduces transmission until the final report is released.

Once I get the COVID-19 vaccine, am I immune forever?

It isn’t clear yet how long immunity lasts after COVID-19 vaccination since vaccines can vary significantly in terms of the duration of their immunity. The measles vaccine, for example, immunizes against measles for life, while the flu vaccine only immunizes against influenza for several months. While scientists hope that COVID-19 vaccines will last at least a couple of years, the duration could be shorter or longer.

“I think, what is clear, is that none of these vaccines are going to be a knockout vaccine, like the polio vaccine, where it's one and done and you don’t have to think about it ever again,” Becerra said.

Unfortunately, only time and additional data can give us a definitive answer to how long COVID-19 vaccine immunity will last.

Do I still need to wear a mask and practice social distancing after I receive the COVID-19 vaccine?

Since it’s not entirely unclear yet how well the COVID-19 vaccines can reduce virus transmission and how long immunity lasts, wearing a mask and practicing social distancing are still important safety measures to help stop the spread of SARS-CoV-2.

“The way you deal with an infectious disease is to stop it from transmitting,” Becerra explained. “We're at a point where we have to think about that, even after vaccinations. Because if the vaccines aren't stopping transmission entirely - that's why we still have to wear masks, that's why we still need social distancing.”

When will things go back to normal?

It may be a while before we can get back to our pre-pandemic lifestyle (especially if that lifestyle involved crowded, maskless social gatherings).

Some health experts predict that life won’t begin to get back to normal until we reach a critical point in the population’s collective immunity. This critical point, known as ‘herd immunity’, is the point at which most of a population is immune to an infectious agent (like a virus) and those who are immune provide indirect protection to those who are not immune.

For COVID-19, experts predict that 70% to 85% of the population will need to be immune to the virus before we reach herd immunity.

Although herd immunity may sound like a light at the end of the tunnel, there are several reasons that herd immunity may be difficult, if not impossible, to achieve.

First, herd immunity assumes that immunization prevents transmission, which may or may not be the case with COVID-19 vaccines.

Second, children and teens make up 22% of the U.S. population and COVID-19 vaccines are not yet approved for these age groups. Until vaccines are approved for children and teens, we won’t likely achieve herd immunity.

Third, our chances of reaching herd immunity are less likely if vaccine-resistant variants arise.

Fourth, many Americans say they don't want to get vaccinated. Vaccine hesitancy alone may make herd immunity an impossible goal.

Despite the many factors stacked against our race toward herd immunity, however, there is another important factor at play: natural immunity.

Recent estimates suggest that 17% of the U.S. population has been infected with COVID-19 since the start of the pandemic. However, given that testing for COVID-19 occurred much less frequently during the early stages of the pandemic, it’s possible that an even greater proportion of the population has had COVID-19. Considering that both natural immunity and vaccinations push us closer toward achieving herd immunity, we may have a chance at achieving it.

But, even if natural immunity and vaccinations aren’t enough to reach herd immunity, Becerra suggests that we shouldn’t panic.

“Here's the thing, we haven't reached herd immunity on many infectious diseases that we don't worry about. We don't necessarily have to reach herd immunity for society to be functional. If vaccines don’t reduce transmission, it will affect what interventions we implement,” Becerra said. “However, it may not reduce the chances of society going back to some kind of normalcy if appropriate public health measures are adhered to.”

Overcoming vaccine hesitancy will be critical to getting back to normalcy

Regardless of whether herd immunity is possible, Becerra stresses that vaccinations are critically important to ending the pandemic, and, unfortunately, vaccine hesitancy is a serious issue.

“I'm very concerned about vaccine hesitancy,” Becerra said. “We are already seeing hesitancy among staff at medical centers, and these are nurses, health care workers, doctors and researchers. There's hesitancy for a number of different reasons. There's the anti-vaxxers of course, but then there's also a lot of just general concern about whether the vaccine development was rushed. There are a lot of ludicrous theories people have with no evidence to support them.”

Becerra also explained that there is no reason, biologically, to expect that the vaccines would be dangerous.

“mRNA degrades in your body,” he said. “It's just like an email telling your body how to fight the virus, and then it just degrades. People have had concerns about previous vaccines because they use live attenuated viruses. These vaccines don’t use attenuated viruses. So, if anything, they might be even safer.”

According to Becerra, overcoming vaccine hesitancy will be key to getting back to our pre-pandemic lifestyle. As he put it, “The reality is that we just need to get these vaccines into arms.”

It is also critical for people to continue wearing face masks and following social distancing guidelines after they are vaccinated. Despite many people viewing the vaccine as a free ticket to maskless socializing, the reality is that we still need to be patient.

As Becerra explains, we might be waiting a couple of years still for things to get back to normal.

“When are we going to be able to go to a football stadium without masks? When can we go out for a drink at a crowded bar? When can we shake the hand of a stranger next to us at a ballgame? It might be a couple of years before any of that, if ever.”

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