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by Elaine K Howley

March 2, 2021

The science behind the pandemic and the efforts to achieve herd immunity

The recent article “COVID-19 Vaccines and Coronavirus Variants: What Swimmers Need to Know” outlines the current state of the coronavirus pandemic and how it’s affecting USMS practices and events. In this this longer version, we’ll dive deeper into the science behind how the coronavirus vaccines work, the current estimates on herd immunity, and how these developments might allow a return to more normal life.

How do the coronavirus vaccines work?

There are three vaccines authorized for emergency use in the U.S., ones manufactured by Pfizer-BioNTech, Moderna, and Johnson & Johnson. The first two require two doses a few weeks apart, and the J&J vaccine is a single shot.

The Pfizer-BioNTech and Moderna vaccines deliver genetic material called messenger RNA, or mRNA, to the body. This snippet of genetic code is used by the cells to manufacture spike proteins that match the structures on the outside of the SARS-CoV-2 virus particle. These are the spikes that give the virus its crown-like appearance and its coronavirus name.

Your immune system learns to recognize these spike proteins as foreign and that triggers an immune response in the body. This is why many people feel run-down, have a fever, or develop other symptoms in the day or two after receiving the shot. Those symptoms are a good thing. They mean your immune system is learning how to protect you from the virus.

Once that immune system memory has been established, your body can successfully fight off the virus if you’re exposed to it later. In studies, some people who received these mRNA vaccines showed a stronger immune response to the virus than people who’d recovered from infection with the virus. Both vaccines have been found to be highly effective (94 to 95 percent) in preventing symptomatic COVID-19 infection after the administration of both doses.

Remember, these side effects are a good thing. They signal that your immune system is responding to the vaccine appropriately and building the antibodies you need to be protected from the virus in the future.

Though there’s little in the way of formal data, anecdotally, many people say the side effects from the second shot tend to be worse than the first. There also seems to be a tendency for these reactions to be stronger in younger people. The theory is that younger people usually have more robust immune systems that produce a stronger response to the vaccine.

But there’s no hard and fast rule as to how you’ll respond. Just be aware that if you’re in your 20s and just had your second dose, you may need to take a couple days off from swimming after the shot to rest. You may feel like you’ve got the flu, and rest and fluids are a good way to help ease some of those symptoms. Folks in their 70s might feel well enough to go to the pool the next day but may not feel so great and need a couple days off.

If side effects increase in severity or you develop an allergic reaction to the vaccine, contact your doctor for guidance.

When will swimming events start up again?

Quite simply, we don’t know yet. It all depends on when we reach so-called herd immunity, or a level of protection against the virus that curbs its transmission. When enough people are immune to the virus, we can resume gatherings, travel, and other swimming-business-as-usual events.

Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, has been incrementally raising his estimates of what percentage of the population will need to be vaccinated to reach that herd immunity threshold.

Early on, the hope was that 60 to 70 percent immunity would be enough, but now, it’s looking like we might need to achieve a higher percentage to stamp out spread of COVID-19. In December, Fauci told The New York Times that “we really don’t know what the real number is. I think the real range is somewhere between 70 to 90 percent. But I’m not going to say 90 percent.”

That said, according to a Feb. 3 report from KHN, Bruce Y. Lee, a professor of health policy and management at the City University of New York, did some calculations working from the idea that 70 percent herd immunity level is the threshold needed to get life more-or-less back to “normal.”

Given that about 330 million people live in the U.S., 70 percent of that figure is 231 million. To fully inoculate all those people will take 462 million doses of the currently available two-dose Pfizer-BioNTech and Moderna vaccines.

If 1 million doses are administered around the country per day, that means about 460 days, a little over 15 months, to achieve that (potentially too low) herd immunity target of 70 percent inoculation. That puts us into spring of 2022.

However, as of Feb. 10, the seven-day average of vaccine doses administered across the U.S. as reported by the Centers for Disease Control and Prevention was about 1.49 million doses per day. As the doses delivered daily increases, the timeline for resumption of normal activities will likely condense.

At all levels, the pressure is on to speed up deployment of vaccines. KHN reports that if the administration of vaccines can climb to 1.9 million shots per day, we’d reach that 70 percent target around Labor Day. If the U.S. can deliver 2.4 million shots daily, that 70 percent goal will be in view around July 4.

As states continue to work out the kinks on their vaccine administration programs, it’s not outrageous to hope that we might be able to gather for some open water events or swim meets later in the summer or sometime in the fall.

When will everyone be vaccinated?

Although rollout of the two available vaccines has been bumpy at best in some parts of the country, progress is being made. On Feb. 18, the CDC reported that about 57.7 million doses of a COVID-19 vaccine have been administered. About 41 million people have received at least one dose of a COVID-19 vaccine, including about 16.2 million people who’ve also received a second dose and have been fully vaccinated.

Some of the challenges associated with these vaccines include the need to keep them very cold, which requires the use of special freezers. Supply scarcity and overcoming vaccine hesitancy in some communities are also difficulties that are being addressed.

The J&J vaccine is a viral vector vaccine that works a little differently from the mRNA vaccines. The J&J shot uses a harmless virus—in this case an adenovirus (from the same family of viruses that’s often responsible for common colds)—to act like a “Trojan Horse” to sneak into cells where it manufactures spike proteins that prime the immune system to be ready in case of exposure to the SARS-CoV-2 virus. J&J has previously used this technology to develop an Ebola vaccine that’s available in Europe.

The J&J vaccine has been found to be 66 percent protective against moderate to severe COVID-19 infection and 85 percent effective in protecting against severe disease. A big plus to the J&J viral vector vaccine is that it confers protection after just one dose. It should be available within the next few weeks and speed up how quickly vaccinations are happening and how quickly we reach herd immunity.

What are coronavirus variants?

Another concerning storyline in this ongoing pandemic is virus’s innate ability to mutate quickly. Every time a virus replicates, that’s an opportunity for a genetic mutation to occur. Because there’s so much virus circulating in the world right now, that means untold trillions of opportunities every day for a stronger, more virulent version of the virus to become the predominant form of the virus in circulation. It’s evolution in real time with real consequences for human health. 

We’re already seeing such variations on the SARS-CoV-2 virus cropping up around the world. The resulting mutant strains are alarming in their ability to circulate more easily and potentially evade vaccines that have been developed for the original strain. Increasingly, it’s believed that some of these variants might be deadlier as well as more easily transmitted.

There are currently three mutated strains public health officials are most concerned about:

  • The U.K. variant. More technically called the B.1.1.7 variant, this strain was first identified in England and has since been discovered in many other countries across Europe and in Australia and North America. In the U.S., it’s now the most widespread of the three variants of most concern, and it could become the dominant strain by early spring.
  • The South African variant. This mutation, known officially as the B.1.351 variant, was first observed in South Africa. It was confirmed in the U.S. in late January. It’s now the dominant strain in South Africa, and in early February, use of a vaccine manufactured by Oxford-AstraZeneca was halted in South Africa when a study indicated that the vaccine was ineffective in preventing mild to moderate illness from this variant. However, that same vaccine has been shown effective against the U.K. variant, which underscores the unpredictability of how these new variants will respond to different vaccines.
  • The Brazil variant. This P.1 variant originated in Brazil and is of grave concern to many public health officials because it’s running rampant through areas of Brazil that had already seen high infection rates and theoretically should have been less vulnerable. This could signal that the mutation makes the virus different enough that the immune system doesn’t recognize it and can’t fend it off.

It’s unclear at this time how much, if any, protection the vaccines can offer against these variants. There just isn’t enough data to be sure yet. Because of that, even if you have been vaccinated, it’s important to continue wearing a mask, washing your hands frequently, and practicing social distancing as you have for the past year to slow the spread and avoid becoming infected with one of these new strains.


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