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March 31, 2021

Answers to Your Burning COVID Vaccine Questions

Answers to Your Burning COVID Vaccine Questions

Updated on March 19, 2021 at 3:30pm EDT.

Confusion is swirling about the coronavirus variants circulating across the U.S. and in other parts of the world. What does this mean for the existing vaccines? Is one better than the others? Will the vaccines that become available in the weeks or months ahead be even more effective? When can we finally stop wearing masks?

Here are some answers to these and other burning questions:

If everyone I know gets vaccinated and I don’t, I’m fine right?
“Not necessarily,” says William Raszka, MD, Pediatric Infectious Disease Specialist at The University of Vermont Medical Center. “We do not yet know if the vaccines prevent transmission or how effective they will be against emerging variants.”

Phase 3 trials for the Pfizer, Moderna, and J&J vaccines only looked at protection against symptomatic COVID. They did not look at how well these vaccines protect against spread among infections that do not cause symptoms.

The only trial that has looked at protection against this asymptomatic transmission was for the Astrazeneca vaccine, which is still under investigation and not currently available in the United States. This trial found that the vaccine reduced positive cases by 67 percent after the first dose and 50 percent after the second dose.

So, if people you know get any of the available COVID vaccines, they could still get asymptomatic COVID, which they could spread to you or others. 

Bottom line: Right now we just don’t know how likely transmission among vaccinated people will be, and it’s probably wise not to take unnecessary risks. To protect yourself, the U.S. Centers for Disease Control and Prevention (CDC) is advising people to get the vaccine that is available to them as soon as they are eligible to receive it.

When, if ever, will social distancing and masks no longer be necessary?
“Personally, I think masking will be here for some time,” says Dr. Raszka. “I do not see those disappearing until we have widespread population level immunity.”

In order to reach herd immunity, experts estimate that about 70 percent of the population needs to become immune to COVID-19, or about 200 million people.

Figuring out when we might reach herd immunity is complicated, Raszka points out. To calculate herd immunity, it’s important to think about the reproduction rate, which is an indication of how easily a microbe gets passed around and causes infection. 

And as viruses become more infectious, the percentage of the population needed to become immune to reach herd immunity may increase. For example, for very contagious viruses like measles, 94 percent of the population needs to be immune to reach herd immunity.

In the meantime, as new, more contagious variants emerge, the percentage needed to reach herd immunity could become a moving target. Getting vaccinated can decrease the likelihood that new variants will emerge and is the safest way to reach herd immunity. Scientists are working on creating newer versions of existing COVID-19 vaccines so that they better protect against current and future variants.

Bottom line: To end social distancing and masks, we will need to get the pandemic under control by reaching herd immunity—the threshold at which the virus can no longer spread easily from person to person. 

Will COVID be a seasonal vaccine that everyone needs to get, like the flu shot?
“That is a hot debate at this time. It will depend on how effective the vaccines are against the variants,” says Raszka.

In late February, the scientific journal Nature published a survey of 119 immunologists, infectious-disease researchers and virologists. Slightly more than one-third said they thought it was likely that the virus could be eliminated from some regions.

But nearly two-thirds of those surveyed disagreed, stating that they expect the virus to become endemic and continue to circulate the world.  In this scenario, the coronavirus would cause limited outbreaks in places where most people are immune and much more disease where most people are not. It could also follow a seasonal pattern, like the flu, and flare up at certain times of year.

Bottom line: It’s unlikely that there will be a dramatic or abrupt end to the pandemic. Many experts predict the coronavirus is here to stay. But like the flu, we can—and will—likely learn to peacefully coexist with it.

So many children are going stir crazy at home with virtual schooling. When can they finally go back to school? And when will they be eligible for the vaccine?
Health officials have relaxed physical distancing rules for children and teens in schools. The CDC updated its guidance, advising that students should maintain a distance of at least 3 feet inside the classroom—not 6 feet as previously recommended.

This move paves the way for a return to in-person learning at schools across the country, which have been forced to keep many students at home either part- or full-time to accommodate the greater space requirements of the more stringent distancing rule.

Right now, Pfizer's vaccine has been authorized for people ages 16-years and up. Moderna and Johnson & Johnson's vaccines are currently authorized for adults ages 18-years and older. 

Johnson & Johnson hasn’t announced clinical trials in children yet. But both Pfizer and Moderna have recently begun testing their vaccines on younger kids.

COVID-19 vaccines could be available to children by fall 2021 or early 2022, according to Anthony Fauci, MD, director of the U.S. National Institute of Allergy and Infectious Diseases.

While those trials are underway, a review of 700 scientific papers found that children are not the main drivers of the pandemic, and that opening schools is not likely to have an impact on COVID-19 death rates among older people.

“I think schools can be made fairly safe in the absence of vaccination,” Raszka argues. “The data is quite clear that there has not been a lot of onward transmission in schools.”

Bottom line: As pediatric COVID-19 vaccine trials continue, many studies have already shown low risk of COVID-19 transmission in schools when appropriate infection control policies are in place.

Does it matter that each dose of Pfizer’s vaccine contains 30 micrograms of vaccine but Moderna went with a much larger dose of vaccine, 100 micrograms? So Moderna is using a little more than three times as much vaccine per person than Pfizer. And yet, they aren’t getting better results—why is that?
Phase 3 trial results showed 95 percent efficacy against COVID-19 for the Pfizer vaccine, known as mRNA-BNT162b2. Meanwhile, the Moderna vaccine, called mRNA-1273, was found to have 94.1 percent efficacy—even though these two vaccines use different dosages.

While both vaccines are mRNA vaccines, they’re not exactly the same. Both carry genetic material that tells your cells to make a coronavirus protein, which triggers an immune response in the body that protects you from COVID-19. But they’ve been formulated slightly differently in the lab.

This translates into other differences between the two vaccines. For example, the recommended amount of time between dose 1 and dose 2 for the Pfizer vaccine is 21 days. Those who get one shot of the Moderna vaccine, however, need to wait 28 days before getting their second dose.

The Pfizer vaccine also needs to be stored at between -112 and -76° Fahrenheit. Before mixing, the vaccine may be stored at between -13 to 5 ° Fahrenheit for up to two weeks.

The Moderna vaccine can be stored at between -13 to 5 ° Fahrenheit, and only requires a normal refrigerator freezer. Vials of this vaccine may be stored in the refrigerator at between 36 and 46° Fahrenheit for up to 30 days before they are punctured.

Bottom line: “The vaccines are different and it is normal for different vaccines or medicines to require different doses,” explains Namandje Bumpus, PhD, Professor of Pharmacology and Molecular Sciences at The Johns Hopkins University School of Medicine. “Since they are different products the dose shouldn’t be directly compared. What is important is knowing that the authorized dose is effective.”

Results from phase 3 trials show that the Moderna mRNA vaccine has 94.1 percent efficacy, the Pfizer mRNA vaccine has 95 percent efficacy. Meanwhile, the Johnson & Johnson vaccine has 66 percent overall efficacy but, in the United States, efficacy jumps to 72 percent. What do these percentages really mean?
Efficacy does not tell you anything about your odds of getting symptomatic COVID-19 after receiving the vaccine.

Terms like efficacy and effectiveness are often used interchangeably, but they mean different things to researchers.

Researchers define efficacy as how well a new medical treatment performs under ideal or controlled conditions, like a clinical trial. It’s actually a rate that’s calculated using a formula. In human trials, it’s the percent reduction in new, symptomatic COVID-19 cases among vaccinated people, compared to people who got the placebo.

For the Moderna vaccine, the proportion of new, symptomatic COVID-19 cases was decreased by 94.1 percent for vaccinated people compared to the placebo group. Similarly, in the Pfizer clinical trial, the proportion of symptomatic coronavirus cases fell by 95 percent among those who received the vaccine compared to the placebo group. For Johnson & Johnson, the proportion of symptomatic coronavirus cases fell by 72 percent in the United States.

“These numbers only refer to the percent reduction in COVID cases between placebo and vaccinated. They do not translate into your chances of getting COVID if you’ve been vaccinated,” explains Bumpus. “They really refer to the clinical trial specifically, not the real world.”

The effectiveness of a new medical treatment describes how well it actually performs in the real world. And various factors can affect vaccine effectiveness, including age or whether or not people get their second dose.

Bottom line:  Efficacy rates are important because trial results give us a fair approximation of how well these vaccines work—even though they still require monitoring in the real world. As more and more people get vaccinated, this data will continue to be collected and give us a better idea of how well these vaccines protect people over time.

Johnson & Johnson says its vaccine has 72 percent efficacy in the United States, 68 percent efficacy in Brazil, and 64 percent efficacy in South Africa.  How can that be? Why does it have lower efficacy in certain places?
COVID-19 genetic variants have emerged in different parts of the world. When trials are conducted in these regions, it may affect vaccine efficacy overall as well as efficacy rates specifically in these countries. 

For example, existing vaccines are less effective against the South African variant known as B1351.

Scientists are most concerned about variants with mutations in the coronavirus’ spike protein—the surface protein it uses to infect cells.  

COVID-19 vaccines have been developed to produce an immune response against this spike protein. COVID-19 variants that have changes in the spike protein look different to immune cells that have been trained to recognize the original spike protein.

Bottom line: New variants in some parts of the world could reduce vaccine efficacy since their spike protein looks different. Investigations on worrisome variants are underway and scientists are already working to update existing vaccines to help cover these mutations.

What's the deal with Novavax? Phase 3 results from the UK showed 89.3 percent efficacy. Why is the percentage so much lower? 
For the Novavax clinical trial in the UK, the proportion of new, symptomatic COVID-19 cases was reduced by 89 percent for vaccinated people compared to the placebo group.

Unlike the Pfizer and Moderna vaccines, Novavax is not an mRNA vaccine. It’s a different type called a protein-subunit vaccine. It uses a harmless lab-made version of the coronavirus spike protein. The vaccine also contains an adjuvant, which is a substance that helps ensure that the immune system jumps into action and starts making protective antibodies.

Protein-subunit vaccines have already been developed to treat other infectious diseases, like whooping cough and shingles, whereas mRNA vaccines, such as those from Pfizer and Moderna, have less of a track record.

It’s not easy to know why the Novavax vaccine showed lower efficacy than the Pfizer or Moderna vaccines.

First, these are different types of vaccines. In addition, trials for these vaccines were conducted at different locations around the world, contained different groups of people, and took place at different times in the pandemic. These differences may also play a role in the efficacy data.

For example, phase 3 trials for both Pfizer and Moderna took place before recent genetic variants of the virus began to emerge, whereas Novavax testing took place after they had emerged.

“As more variants emerge, it looks like efficacy is lower for certain vaccines. We don’t know how earlier vaccines [like Pfizer and Moderna’s mRNA vaccines] would have performed in those settings yet,” Bumpus says.

Bottom line: Comparing the efficacy rates for different vaccines is a little like comparing apples to oranges. What is clear is that all three vaccines currently available in the United States prevent hospitalizations and death from COVID-19.

Oxford and AstraZeneca say their vaccine has 82 percent efficacy after the second dose. Johnson & Johnson (J&J) says its single-shot vaccine has 66 percent overall efficacy against moderate to severe COVID-19. Why not get both? Wouldn’t that add up to more than 100 percent efficacy?
“Unfortunately, that’s not how efficacy works” explains Bumpus. “Efficacy rates alone do not tell us the odds of infection or how well combinations of vaccines would work,” he says. “Importantly, we don’t know anything about the safety of doubling up on these vaccines.”

Efficacy is a rate, and you can’t simply add up these rates to reach 100 percent. It’s not how the math works.

When researchers combine rates from different studies, they use complicated statistical techniques that take into account differences within and between studies. 

Currently, the CDC is advising against mixing and matching vaccines. Combining different vaccines, however, is under investigation as a possible way to deal with vaccine shortages, logistical issues with the largest vaccine rollout in history, and perhaps increase protection against new variants.

Bottom line: The safety and efficacy of being vaccinated with more than one type of COVID-19 vaccine is being explored but has not yet been established. Currently, health officials advise that people fully vaccinate with the same vaccine product.

Which vaccine is best, and can I choose which one I get?
The short answer is that we don’t know yet which vaccine works best. As variants emerge, the U.S. Food and Drug Administration (FDA) and scientists are working to tweak existing vaccines to provide better protection against mutations.

At this point, people are unable to choose which vaccine they want to get. Right now, doctors are advising everyone who is eligible to get vaccinated with the shot that is offered to them.

“What is important is getting vaccinated. Data about the effectiveness against variants is still developing,” Bumpus advises. “An advantage of the technologies being employed in these vaccines is that there is an ability to develop vaccines that are specifically aimed at protection against variants that emerge.”

Given the sheer magnitude of the rollout, there are also logistical hurdles to consider. The fact that the J&J vaccine requires just one dose is one advantage. The fact that this vaccine relies on a harmless virus to deliver the genetic code for the coronavirus protein that will trigger an immune response means also means that it’s easier to store and ship than the Pfizer or Moderna mRNA vaccines. J&J's vaccine also has milder side effects than Pfizer and Moderna, accoridng to the U.S. Food and Drug Administration (FDA). 

Bottom line: The authorized COVID-19 vaccines all provide significant protection against the disease and save lives. And the coronavirus will have fewer opportunities to mutate as more people are vaccinated and we inch closer to herd immunity.

Medically reviewed in March 2021.

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