内容摘要：You might wonder which Covid vaccine is the "best."But there's no inferior choice. All the FDA-autho

You might wonder which Covid vaccine is the "best."

But there's no inferior choice. All the FDA-authorized vaccines (there are currently three) are outstanding options, according to infectious disease experts. Why?

"All of them look great at preventing disease that results in hospitalization and death," emphasized Dr. Thomas Russo, the chief of infectious disease at the University of Buffalo's Jacobs School of Medicine and Biomedical Sciences.

Here's what to know.

The vaccines are all effective

Numbers, without context, can be misleading.

The Pfizer and Moderna vaccines, both excellent options, showed around a 95 percent efficacy, which essentially means the vaccine prevented Covid infections in 95 percent of people tested (among tens of thousands of participants), compared to people who didn't get the vaccine in the trials. Any public health expert would say those are impressive, if not amazing, results.

In the U.S., the Johnson & Johnson vaccine showed a 72 percent efficacy. These are also impressive results, but should they be viewed as "worse" than the Pfizer and Moderna vaccines (which are a new type of vaccine known as mRNA vaccines)? No.

These efficacy figures don't do a good job of communicating hugely important numbers. An important number is how well the vaccines prevent severe, critical disease — the type of disease that hospitalizes people, allows the virus to flourish and mutate in the body, and can kill.

Good news: In their respective clinical trials, all threevaccines prevented this severity of disease. No one given the Johnson & Johnson shot died or was hospitalized (this includes people in South Africa where a nasty, highly infectious strain is circulating). No one given the Pfizer and Moderna vaccines died or were hospitalized, either. What's more, all the vaccines greatly lowered the risk of severe symptoms, like pneumonia and breathing trouble.

"All three vaccines are very effective," said Dr. Renuga Vivekanandan, the assistant dean at the Creighton University School of Medicine. "The goal is to prevent hospitalization and death. All three vaccines are very effective in achieving this goal," she said, noting that Johnson and Johnson had over 40,000 participants in its clinical trials.

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So attempting to "choose" a vaccine or belaboring the best option simply isn't prudent right now. The Johnson & Johnson vaccine protects against the worst Covid outcomes, while also providing high levels of immunity against infections.

"Comparing the efficacies right now is a moot point," said Mark Cameron, an immunologist at Case Western Reserve University who previously helped contain the outbreak of another deadly coronavirus, SARS, in 2003. "Right now the point is breaking the chains of transmissions through any means and saving lives. All three vaccines have the same potential to save lives."

"All three vaccines have the same potential to save lives."

All three vaccines produce enough of an immune response — meaning they limit the spread of virus particles in the body and generally keep the virus at bay — to limit terrible symptoms and extreme harm to one's lungs.

It's worth knowing that comparing these vaccines' efficacy is not the most straightforward or simple exercise, anyways. Importantly, vaccine efficacies can change over time. There's evidence the Johnson & Johnson vaccine increasesits efficacy against severe disease (at least in the short term according to available data) to well over 90 percent during the 56 days after vaccination. It's also possible the timing of when the clinical trials happened has impacted efficacy results for the vaccines. Johnson & Johnson conducted its big trials in the fall and into the winter, later than the mRNA vaccines. At the time, different, more infectious coronavirus variants were circulating around the population andinfections were both rising and nearing their grim peak in places like the U.S.

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"It's really an apples to oranges comparison," said the University of Buffalo's Russo. He noted that Johnson & Johnson and the mRNA vaccines may in reality have somewhat similar efficacy numbers. Yet, even so, these numbers aren't written in stone.

Vaccinate now, tweak later

The Covid vaccine you get is not the end of your vaccine story. It's unknown how long immunity will last, but infectious disease experts are watching vigilantly. The vaccines may provide strong immunity for years. Some might provide longer immunity than others. It's possible "booster shots," another vaccine meant to boost immunity or provide improved immunity against newer coronavirus strains, will be needed.

"Long-term immunity is still an unwritten chapter for these vaccines," emphasized Cameron, noting drugmakers are already working on booster shots. "The study of a vaccine's safety and efficacy doesn't stop when the vaccine is released. It continues."

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In the coming year, we'll hear about new strains or variants of the virus. That's normal and expected, especially considering this microbe is the most intensely observed virus ever. "It's constantly changing," said Brian Labus, a public health expert at the University of Nevada, Las Vegas. While mutations can make a virus more transmissible or potentially decrease the effectiveness of a vaccine, they certainly won't suddenly render a vaccine useless. "You might have slightly reduced efficacy, but one small mutation doesn’t make it ineffective," said Labus. The Johnson and Johnson vaccine, for example, has a 64 percent efficacy for the South African variant, a highly transmissible strain, yet it's still highly effective against severe symptoms from this strain (over 80 percent), and in trials completely protected people against hospitalization and death.

For 2021, public health experts emphasize taking advantage of the outstanding vaccine candidates available now, whatever they are (in the past, it took at least yearsto produce such effective vaccines for diseases). Yes, in the coming years, the Covid vaccines may be tweaked. That's OK. Flu vaccines, for example, are tweaked every year.

"Vaccinate now, tweak later," said Cameron.

See Also: How you'll know the COVID-19 vaccines are safe

Attempting to wait for or "choose" a vaccine won't help end the pandemic, or provide protection. "You should be comfortable getting whatever vaccine is available to you," said Labus.

The greater goal is to give the virus nowhere to go. When enough people have high amounts of immunity, the virus can't break out in the population, which is called herd immunity. The virus meets bodies it either can't infect, or can't infect well. All of the vaccines can help us achieve herd immunity relatively quickly, particularly ones that only require one dose (like Johnson & Johnson).

"No one vaccine will be responsible for that victory," said Cameron.