Coronavirus Briefing: What Happened Today

Answers to common questions about mixing and matching vaccine doses.,

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This is the Coronavirus Briefing, an informed guide to the pandemic. Sign up here to get this newsletter in your inbox.

ImageDaily reported coronavirus cases in the United States, seven-day average.
Daily reported coronavirus cases in the United States, seven-day average.Credit…The New York Times

The F.D.A. seems likely to allow Americans to switch Covid vaccines when choosing a booster in a decision that is expected later this week. Scientists have been experimenting with the mix-and-match strategy for years, and they have long suspected that a combination of different authorized vaccines may sometimes work better than two identical doses.

My colleague Carl Zimmer answered some common questions about mixing and matching shots.

How does mix-and-match work?

We have data from other vaccines — for example, experimental H.I.V. vaccines — that suggest that mixing vaccines could create a broader, more potent response than multiple doses of a single vaccine. Different types stimulate the immune system in different ways, and switching between two vaccines might give people the best of both worlds.

What do we know about mixing Covid vaccines?

The pandemic gave scientists new opportunities to test the mix-and-match idea. Young people in Europe who had received one dose of AstraZeneca were offered a second dose of Pfizer because of a small but real risk of blood clots. The two vaccines are profoundly different, but when researchers looked at the immune response from this mix-and-match approach, they found that it produced more antibodies than two shots of AstraZeneca alone.

How well do they work?

In June, the National Institutes of Health started its own variation on the experiment in Europe, looking at what happens when fully vaccinated people switch to a new vaccine for a booster. Researchers recruited people who had gotten one of the three vaccines authorized in the U.S., and then gave them one of the three vaccines as a booster. The scientists found that switching boosters raised the level of coronavirus antibodies, no matter which combination people got. And switching to a new booster did not produce any notable side effects.

The results for people who initially received a Johnson & Johnson vaccine were particularly striking. Those receiving a J.&J. booster saw antibodies go up just fourfold. Switching to a Pfizer-BioNTech booster raised antibody levels by a factor of 35. A Moderna booster raised them 76-fold.

Will there be other booster options?

It’s entirely possible. Over 100 Covid-19 vaccines are now in clinical trials, and some of those new vaccines could prove to be superior boosters. It’s not yet clear how many Covid-19 boosters we will need to gain long-lasting protection. It’s conceivable that a single shot may be enough. But it’s also possible that Covid-19 vaccines will have to be given every year, much like a seasonal flu shot.

If Covid-19 boosters become an annual event, then a mix-and-match strategy should help enable more people to get vaccinated. It will be far easier for people to get regularly immunized if they don’t have to worry about receiving another shot of their original vaccine.

The flu offers a precedent for this plan. Each year, vaccine makers produce new batches of seasonal flu shots. Some are inactivated influenza viruses. Some contain live viruses that are too weak to make people sick. Others are made just of influenza proteins. The C.D.C. has no preference for which age-appropriate flu vaccine people get. That sort of flexibility may also drive down the price of boosters.


Italy set a new bar for major Western democracies when it put in place a sweeping new law last week that requires the country’s entire work force — public and private — to show proof of vaccination, a negative coronavirus test or recent recovery from Covid-19.

The government-issued Green Passes must be displayed to enter offices, schools, hospitals or other work places. Those who do not have a pass must take unpaid leave, and workers risk fines of up to 1,500 euros ($1,760) for not complying.

In the initial days after the law went into effect, there were sporadic protests and some lawmakers “occupied” their offices in protest, but the demonstrations were smaller than previous protests against vaccines. More than anything, they seemed to underscore that the Green Pass was now a fact of Italian life. More than 80 percent of people in Italy over age 12 are now fully vaccinated against Covid.

Government officials say that the measure is already working, and that more than 500,000 previously reluctant people — much higher than expected — have gotten inoculated since the government announced its plan last month.


For many of us, the pandemic offered us the opportunity to rethink our lives: how we work, eat, sleep, connect with others and spend our free time.

It was also a break from our regular habits and the old way of doing things. In many ways, the pandemic has given us permission to change who we are by leaving behind the parts of our lives that never felt exactly right in the first place.

For some, that may mean giving up after-hours work emails or Slack messages, or abandoning a stoic attitude and being honest about self-care, or letting go of some social anxiety by saying “no” to more events.

Whatever those things are for you, we’d love to hear about them. We’re asking readers: What are the things you’re giving up as we slowly emerge from the pandemic?

We may use your response in an upcoming newsletter. If you’d like to participate, you can fill out this form here.



I am a nurse practitioner who will stop working in health care for the first time in 20 years and start my new full time job as “Home Manager.” The mounting pressure by administration to do more with less finally broke this caregiver’s back. I will now get to raise my children without the increased risk of exposing them from my work. My mom once said: “Work is like having your hand in a pail of water. Remove your hand and work still goes on.” My hand is out … now holding my child’s instead.

— Jenn Murty, Eau Claire, Wis.

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