5 New Things We Learned About COVID-19 In March 2021

Can you spread the virus after you've been vaccinated? Can you get the coronavirus twice? Here's what we know now.
Several European countries paused their rollout of the AstraZeneca vaccine in March, but have since resumed.
LENNART PREISS via Getty Images
Several European countries paused their rollout of the AstraZeneca vaccine in March, but have since resumed.

What we know about COVID-19 seems to change by the minute.

It’s understandable, given the massive scale of the pandemic. Right now, more than 129 million cases have been confirmed around the world. And even a year into the pandemic, the virus and ways to address it are still relatively new to the medical world, so researchers are learning as they go.

The amount of information out there about the coronavirus is dizzying. It’s hard to keep track of what’s known, what’s a myth and what guidance we should follow. That’s why we’ve rounded up five of the most important new things we learned about COVID-19 in March:

1. The Pfizer vaccine protects kids as young as 12.

In late March, Pfizer announced results from a study of roughly 2,000 children between the ages of 12 and 15 who received both doses of its vaccine. The findings showed that the vaccine was 100% effective at preventing COVID-19 among participants, and any side effects children experienced after vaccination were in line with what’s expected in adults.

The study, which has not yet been published, gave a lot of hope to pediatricians, public health officials and many parents who are eager for children to get vaccinated.

But it’s just one step. Pfizer has said it plans to submit an emergency use authorization request for kids ages 12 and up “in the coming weeks,” and its CEO said the company hopes to start vaccinating children in that age group before the fall. Other vaccine manufacturers are also forging ahead. Moderna is studying its vaccine in children between the ages of 12 and 17, and Johnson & Johnson intends to begin studying its shot in kids soon as well. So far, young children have been left out of trials.

Questions about children’s vaccination matter not just for individual kids and their families, but for the overall course of the pandemic. As a Scientific American article put it earlier this week, “Given that most kids are at low risk for complications from COVID, the need for a pediatric vaccine for the disease may not seem pressing. But scientists say the pandemic may never be fully controlled until kids are inoculated.”

2. The vaccine *might* help COVID-19 long-haulers.

A lot of mystery still remains around long COVID-19, or ongoing symptoms of the disease that linger even after the initial acute infection.

It’s unclear why some people develop what can be debilitating symptoms that last for months while others bounce back from COVID-19 fairly quickly. It’s also unclear just how prevalent long COVID-19 is, with estimates suggesting it affects 10% to 20% of those who catch the virus — although again, those are just best guesses.

But March brought a glimmer of hope to long-haulers wading through all that murkiness, as recent surveys suggest that getting a vaccine may help relieve symptoms. An informal poll from the Facebook group Survivor Corps found that 36% of people with long COVID-19 symptoms said they’d noticed improvements in how they were feeling post-vaccination. Meanwhile, a small, non-peer-reviewed study published last month found that about a quarter of COVID-19 long-haulers who were vaccinated saw an “increase in symptom resolution.

Again, those surveys and studies are small and far from being scientifically conclusive, but researchers are hopeful that the vaccines could truly help some long-haulers feel better.

“We have anecdotes, we’d love it to be true, let’s wait for some real data,” one immunologist told NPR.

3. COVID-19 reinfection is rare.

The first large-scale study on COVID-19 reinfection was published in March, and it generally offered some pretty good news: The vast majority of people who have had COVID-19 are protected from catching it again for at least six months.

But people ages 65 and older are much more likely than younger individuals to experience repeat infection, according to the study.

Indeed, for younger adults, getting the coronavirus once provided roughly 80% protection against reinfection. But for those 65 and up, it provided only about 47% protection against getting COVID-19 again. All of this makes it very clear that older adults must continue to be prioritized in global vaccination efforts, the study’s authors argued.

4. The Pfizer and Moderna vaccines hold up really well in “real-world” conditions.

A study by the Centers for Disease Control and Prevention released in late March received a lot of attention for its promising conclusion that the two-dose Pfizer and Moderna vaccines are 90% effective at preventing COVID-19 infections in real-world settings.

The study also found that just the first dose of either vaccine was roughly 80% effective at preventing infection about two weeks after receiving it.

Those new findings were important for several reasons: First, they helped confirm that the high efficacy rates demonstrated in earlier clinical trials held up in real life, as CDC researchers tracked nearly 4,000 health care workers, first responders and essential workers.

The findings also empowered CDC officials to state pretty confidently that immunized individuals cannot carry or transmit the virus to others. So they don’t pose a risk to those who have not been fully vaccinated.

On the heels of that study, Pfizer released new data suggesting that its vaccine was 91% effective at preventing COVID-19 infection for six months after an individual receives the second dose — and 100% effective at preventing severe disease. No one knows definitively how long vaccine immunity might last beyond that, but what we’re seeing in this timeframe is at least positive news.

5. AstraZeneca revised its data — again.

March was a pretty messy PR month for AstraZeneca. The company had to revise its efficacy numbers more than once after getting into hot water with health officials for using outdated data in its earlier analyses. AstraZeneca now says its vaccine is 76% effective at preventing COVID-19 infection and 100% effective at preventing severe disease. Those revised numbers aren’t actually all that different from what the company initially released, but the changing estimates have created a bit of confusion.

Also in March, several European countries momentarily paused their rollout of the AstraZeneca vaccine after some people who were inoculated said they’d developed blood clots. The European Medicines Agency also conducted an initial investigation of possible side effects, concluding that the vaccine is “safe and effective.” Those countries have since resumed using the AstraZeneca vaccine. However, Canada announced earlier this week that it had stopped giving the vaccine to those ages 55 and younger.

Ultimately, the efficacy rate for the AstraZeneca vaccine is very good, and experts say the blood clot issues are most likely not directly related, although the possibility cannot be ruled out altogether. Also, Europe’s vaccine rollout has been slow and cases there are rising, so there is a pressing need to get millions more vaccines into people’s arms — and fast. That may be even harder to do, however, as AstraZeneca’s tough month has hurt public trust in the vaccine.

“We still can’t be sure whether this blood disorder is triggered by vaccination, and we don’t know yet whether the risk — if it’s real — applies equally to all recipients, or only to a subset that might be predisposed,” scientist Hilda Bastian wrote in The Atlantic. “In light of these uncertainties, the balance here between vaccination’s costs and benefits is obvious. Given the present context of COVID-19 transmission throughout Europe, and even assuming the very worst about the risk that the AstraZeneca vaccine might pose, the shot will save many more lives per million doses than it could ever possibly end.”

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.

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