Many Americans are excited to get vaccinated against the new coronavirus so they can resume their pre-pandemic "normal" lives, but scientists say even with a vaccine, it may not be safe to resume many pre-pandemic activities just yet, Claire Cain Miller reports for the New York Times' "The Upshot."

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Why getting vaccinated doesn't mean it's safe to resume your pre-pandemic life

According to scientists, there are many reasons why getting vaccinated against the new coronavirus doesn't mean Americans can instantly return to their pre-pandemic normal lives. Perhaps the biggest reason, according to scientists, is that some vaccines don't provide people with perfect immunity against a virus, and that could be the case with America's newly authorized vaccines.

Early data has shown that authorized vaccines from Pfizer and BioNTech, as well as Moderna, can reduce a person's risk of developing Covid-19, the disease caused by the novel coronavirus, by about 95%. While that is a relatively high efficacy rate, it means that a small fraction of people who have been vaccinated, about 5%, could become sick—and that could represent a large number of people if the coronavirus is widespread.

As Ashish Jha, dean of Brown University's School of Public Health, told "The Upshot," "Five percent of a really high number is still a high number, and what you want is 5 percent of a relatively medium or low number."

Further, while some early data suggests the newly authorized vaccines might curb the coronavirus's transmission, it's not yet clear whether the vaccines completely prevents people from becoming infected with and potentially transmitting the novel coronavirus. As such, even if people have received the vaccine, they still may be able to spread the novel coronavirus to others who haven't yet been vaccinated, particularly those who have not been vaccinated for health reasons.

Ultimately, that means people will still have to take precautions to protect themselves and others against the coronavirus, such as wearing face masks, after they've been vaccinated, experts say. According to scientists, the coronavirus's spread likely won't slow down until a majority of Americans have either been vaccinated or have survived a natural infection from the virus.

As a result, Uma Karmarkar, a neuroeconomist at the University of California-San Diego, said Americans should plan how they're going to move forward with their lives in incremental steps after they're vaccinated, rather than returning to their pre-pandemic normal right away.

So what is safer to resume once you've been vaccinated?

Experts say that the risk of contracting the novel coronavirus and developing Covid-19 from doing daily activities such as going to the grocery store generally will be lower for people who've been vaccinated, "The Upshot" reports. However, they caution that until a majority of Americans have been vaccinated, people's lives should remain virtually unchanged for at least a week or two after they've received their final doses of a vaccine, according to "The Upshot." Both the Pfizer and Moderna vaccine are administered in two doses.

And even after those first few weeks, people who've been vaccinated should continue wearing face masks, steering clear of large crowds, and avoiding indoor gatherings when possible, experts say. Further, if you've been vaccinated but your friends and family haven't, current evidence suggests it may possible for you to transmit the coronavirus to them—so it's a good idea to continue avoiding close contact with anyone who doesn't live in your household, according to experts.

In an informal survey of 700 epidemiologist recently conducted by the Times, less than one-third of the respondents said they'd change their behavior after getting vaccinated themselves, and 50% of respondents said they would wait until at least 70% of the population is vaccinated before they change their behavior.

Similarly, Kelsey Vandersteen, a trauma ICU nurse at UW Health University Hospital, told "The Upshot" that she plans to continue practicing behaviors intended to mitigate the coronavirus's spread after she's received a vaccine.

Is it safe to gather once your family and friends have been vaccinated, too?

If you and your family and friends are all able to be vaccinated, it's likely relatively low-risk to resume socializing with them in small groups and indoors, experts say, but it still will be risky to gather in large groups.

At that point, Eric Lofgren, an infectious disease epidemiologist at Washington State University, said he would feel safe resuming in-person board game nights and one-on-one meetings with his students, but he wouldn't yet feel safe taking a flight or going to the movies, because there would be no way to tell whether the people around him had also been vaccinated. 

"Immunity is not an on/off switch; it's a dial," Lofgren said. "If you're below herd immunity, the virus is still happily circulating in the population and there's always a chance the vaccine isn't working for you."

What will be safe to resume once most Americans are vaccinated?

Once a majority of Americans have been vaccinated against the new coronavirus, it will be safer for people to once again eat at restaurants indoors, attend parties, ride a bus, and gather for the holidays, scientists say.

Many experts believe that these activities will be relatively safe to resume once at least 70% of Americans are vaccinated or have recovered from a coronavirus infection, at which point many scientists say that the United States will have reached herd immunity and the coronavirus will no longer spread easily, "The Upshot" reports. However, according to "The Upshot," it's too early to tell when the United States will reach that threshold, because scientists are still unsure how the newly authorized vaccines will affect the coronavirus's contagiousness.

In addition, scientists say it's unclear when the United States will have the vaccine doses needed to vaccinate the hundreds of millions of Americans it could take to meet the heard immunity threshold. Federal officials estimate they'll be able to do so by next summer, but that will largely depend on Americans' willingness to get vaccinated, as well as certain logistical and supply challenges, "The Upshot" reports (Cain Miller et al., New York Times, 12/21).