What to know about restrictions after COVID-19 vaccination

There is no scientific consensus on the extent to which vaccinated people can safely relax physical distancing and other virus-prevention measures. The range of expert opinions is from somewhat to not yet.

Dr. Mitchell Katz, who is in charge of New York City’s public hospitals and has helped set citywide pandemic policy, recalled Monday what he counseled his own father, age 98, and mother, 93.

"They are going to get their second vaccine this week, and I’ve told them that 10 days after they have gotten their second vaccine," their children whom "they haven't been able to visit with because they are a part of separate households can now come and see them, and that they can see other friends of theirs who have been vaccinated."

Still, he said, "when they go out, they still need to wear a mask and use other precautions."

That is because it’s unknown whether those who are inoculated themselves from the virus are still able to spread it to others.

Dr. Jay Varma, Mayor Bill de Blasio’s senior adviser for the pandemic, takes a more conservative approach: "At the current time, we really do recommend that people continue to observe all the things that we're recommending, but it is very likely in the near future when more people are vaccinated and disease rates have come down, we can alter our recommendations," he said.

Varma added: "We have a recommendation for today, and we're going to have a recommendation so it’s going to change probably in the very near future."

How little consensus is there? Varma and Katz gave these somewhat contrasting answers at the same news conference.

On Feb. 10, the CDC said that someone who's been fully vaccinated but has been exposed to someone with suspected or confirmed COVID-19 doesn't need to quarantine if:

• It's been at least two weeks following the second dose in the two-dose series;
• It's within three months of that second dose;
• The vaccinated person shows no symptoms of COVID-19.

And on Feb. 11, the New York State government added an exception to its quarantine mandate for people who meet these CDC criteria. The statement did not address whether a person who travels to a COVID-19 hotspot must continue to quarantine.

With each vaccine available in the United States — Moderna and Pfizer/BioNTech — maximum immunity is conferred 10 to 14 days after the second of two doses, Varma said. Protection is estimated to be 94% effective after the second dose. After the first, it’s as high as 50%.

Much remains unknown about the coronavirus, including how it spreads. It’s not certain whether vaccination stops what is called "onward transmission" of the virus. The question is being studied now, according to the MIT Technology Review: To test the question, the nasal cavities of people who were part of clinical trials last year for the vaccine are being periodically swabbed.

"There are three things a vaccine can do: stop you from acquiring the disease altogether, stop onward transmission, and stop symptoms," Jeffrey Shaman, a public health researcher at Columbia University, told the publication: while some "perfect" vaccines confer "sterilizing" immunity — meaning a virus is prevented from infecting your body altogether — other vaccines allow low-level infection that the immune system then fights off.

It’s 95% lower than before, but yes. There is still a chance that even a vaccinated person could get sick while the virus is widespread, Dr. Ashish Jha, a physician and the dean of the School of Public Health at Brown University, told The New York Times.

"Five percent of a really high number is still a high number," he said, "and what you want is 5 percent of a relatively medium or low number."

That is yet another unknown. "At this point, we're not sure if immunity will last a year or 10 years, or if there will be a need for a booster shot at some point," according to an advisory from the University of California, Davis, Medical Center.

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