Covid-19 Live Updates: U.S. Vaccinations Gather Speed, as Threat of Variants Grows

Vaccinations in the United States are slowly picking up speed as the Biden administration pushes to accelerate inoculations and blunt the spread of more contagious virus variants.

The United States has administered about 30 million doses, and, as of Sunday, is averaging more than 1.3 million doses administered over the past seven days, compared with an average of less than one million per day two weeks earlier, according to a New York Times vaccine tracker.

President Biden, under pressure to speed up coronavirus vaccinations, has recently suggested the nation could soon reach an average of 1.5 million shots a day.

But just as there are signs of progress, another problem has taken root: the spread of the variants, which scientists warn must be contained before they become dominant. Several hundred cases of the more contagious variant discovered in Britain, which experts have said could be the dominant form in the United States by March, have already been confirmed.

The country has also recorded its first two cases of the variant spreading rapidly in South Africa, which has proved to reduce the effectiveness of vaccines.

“If we didn’t have these variants looming,” we would be in a good place, said Dr. Peter Hotez, a vaccine scientist and pediatrician at Baylor College of Medicine in Houston. If those variants take over by spring, “as many of us are predicting,” he said, “it changes everything. Now, we really have to vaccinate the American population by late spring, early summer.”

Two key challenges in the weeks ahead are “increasing the supply of vaccines” and “speeding up the time it takes to administer them,” Andy Slavitt, a White House adviser, said in a news briefing on Friday. Many experts have pushed for bringing other vaccine options out and releasing the first doses more widely.

The most effective state programs, said Dr. Ashish Jha, the dean of the Brown University School of Public Health, are “very simple, age-based, not a lot of complex rules. They focus on getting the vaccines out.”

Here is a snapshot of how five of the best-performing states are doing:

• West Virginia has given at least one dose to 10.7 percent of its population, second only to Alaska, and leads the nation in the percentage of its population that has received two doses (3.7 percent). Early on, the state got a head start because it opted out of a federal program to vaccinate people in nursing homes and other long-term care facilities. While other states chose the federal plan, which teamed with Walgreens and CVS, officials decided the idea made little sense in West Virginia, where many communities are miles from the nearest chain store, and about half of pharmacies are independently owned. Instead the state created a network of pharmacies, pairing them with about 200 long-term care facilities.

• According to health officials in Alaska, there are several reasons behind the state’s relatively high vaccination rate, The Anchorage Daily News has reported. Those factors include: the state’s having received a high number of doses through the Indian Health Service; the decision to receive doses monthly, versus weekly, as most states do; and declining virus caseloads, which has allowed health care workers to focus on inoculations. The state has vaccinated 13 percent of its population, according to a Times database.

• North Dakota has used 91 percent of the vaccines distributed to the state, according to the Times vaccine tracker. It is the only state above 90 percent; more populous states like California (58 percent) and New York (64 percent) have used less, proportionally. North Dakota was among the first states to lower the minimum age eligible for vaccination, from 75 to 65.

• In a recent interview with the American Medical Association, health officials in New Mexico attributed part of the state’s success to its “data-oriented and science-oriented” governor, Michelle Lujan Grisham, and to an app that allowed easy registration and close coordination among hospitals and providers. The state has given 9.8 percent of residents at least one shot, and has used 83 percent of its doses.

• Connecticut got mass vaccination sites up and running early, and uses an inventory system that allocates unused doses to places that need them. But older residents have complained about long waits.

PARIS — Public frustration with lockdowns is palpable across Europe, with pensioners protesting this weekend in Vienna, restaurateurs taking to the streets in Budapest and demonstrators clashing with the police in Belgium, prompting dozens of arrests. The Dutch authorities fined more than 10,000 people last week for violating the national curfew.

While none of the protests resulted in the kind of violence seen in the Netherlands in recent weeks, they reflect a growing impatience as political leaders extend restrictions to guard against a resurgence of the virus fueled by new variants.

In France, President Emmanuel Macron has resisted a full lockdown, making a calculated gamble that his government can tighten the rules just enough to avoid a new wave of infections.

Prime Minister Jean Castex appeared in front of television cameras for an unexpected statement on Friday night, announcing a handful of new curbs, including strict border closures.

“Even if the path is very narrow, we must take it,” Mr. Macron was reported to have said at a cabinet meeting last week, according to the Journal du Dimanche, pushing back against the advice of several senior aides. According to the newspaper, he added: “When you are French, you have all you need to get by, as long as you dare to try.”

Polls in France have shown weariness with restrictions, and grumbling about the rules is growing in some quarters.

France is still under a 6 p.m. to 6 a.m. curfew, and places like cafes, museums and theaters are closed. Schools and shops are open.

After a widely publicized breach of the rules at a restaurant in the southern city of Nice last week and a call to “civil disobedience” by some restaurant owners, the French economy minister, Bruno Le Maire, warned on Monday that any establishments that flouted the rules would be cut off from coronavirus aid.

In the French Alps, protesters blocked roads on Monday to demand that ski lifts reopen.

Critics say that Mr. Macron’s approach may simply be delaying the inevitable and that he could be forced to change course if cases started to surge.

“It’s a risk, I’m hoping it was a calculated risk,” Karine Lacombe, an infectious-disease specialist, told the French news channel LCI on Sunday.

Mr. Macron’s plan is rooted partly in the relative stability of the pandemic in France. The number of new daily cases has inched up only slowly and while hospitalizations remain high, there has been no sudden surge. More contagious variants of the virus have been registered in the country, but the authorities say they believe that their spread, so far, is under control.

“Everything suggests that a new wave could occur because of the variant,” Olivier Véran, the French health minister, told the Journal du Dimanche. “But perhaps we can avoid it thanks to the measures that we decided early and that the French people are respecting.”

Aurelian Breeden reported from Paris, and Marc Santora from London.

Mayor Bill de Blasio of New York said on Monday that coronavirus vaccinations scheduled for Tuesday would be postponed because of the winter storm, the second day in a row that they have been delayed.

Heavy snow was also complicating vaccination efforts in Washington, Philadelphia, New Jersey and elsewhere.

At a news conference on Monday, Mr. de Blasio of New York City said he did not want older residents traveling to vaccine appointments amid blizzard-like conditions with gusty winds.

“Based on what we are seeing right now, we believe tomorrow, getting around the city will be difficult,” Mr. de Blasio said. “It will be icy, it will be treacherous.”

He said he believed the city could quickly make up the appointments later in the week.

“We have a vast amount of capacity; we don’t have enough vaccine,” he said. “We’ll simply use the days later in the week, crank up those schedules, get people rescheduled into those days.”

The storm will temporarily derail a vaccine rollout that has been plagued by inadequate supply, buggy sign-up systems and confusion over the New York State’s strict eligibility guidelines. The vaccine is available to residents 65 and older as well as a wide range of workers designated “essential.”

About 800,000 doses have been administered so far in the city, Mr. de Blasio said.

Vaccine appointments originally scheduled for Monday at several sites in the region — the Javits Center in Manhattan, the Aqueduct Racetrack in Queens, a drive-through site at Jones Beach in Long Island, SUNY Stony Brook and the Westchester County Center — would be rescheduled for this week, according to a statement from Melissa DeRosa, a top aide to Gov. Andrew M. Cuomo. “We ask all New Yorkers to monitor the weather and stay off the roads tomorrow so our crews and first responders can safely do their jobs,” she said.

In the Philadelphia area, city-run testing and vaccine sites were closed on Monday. Connecticut, New Jersey, Rhode Island and parts of the Washington, D.C., area were following suit. Some areas away from the center of the storm were expected to remain open for vaccinations, including parts of Massachusetts and upstate New York.

BERLIN — As Germany’s leaders gather in Berlin to discuss the lagging vaccinations in the country and across the European Union, the bloc got some good news Monday morning when the pharmaceutical company BioNTech announced that it would make 75 million extra doses available in coming months.

BioNTech, a German company, helped develop the first Covid vaccine to be approved in the European Union. It had previously come under fire for admitting, just weeks after the beginning of the bloc’s vaccination drive, that it could temporarily deliver fewer doses than promised because of an upgrade at a production facility in Puurs, Belgium.

But the company will soon be producing shots at 13 different locations, including a new site in Marburg, Germany, Sierk Poetting, BioNTech’s chief operating officer, said in a statement on Monday.

And the British-Swedish pharmaceutical company AstraZeneca, which has also come under criticism for not fulfilling European orders in a timely fashion, has agreed to deliver 40 million more doses by June, Ursula von der Leyen, the president of the European Commission, announced in a tweet on Sunday. That would be nine million more than originally planned.

At a virtual meeting on Monday to address criticism over the slow start of the rollout, Chancellor Angela Merkel of Germany was set to speak with national ministers, state governors, and representatives from the pharmaceutical industry.

Since vaccines began to receive approval in the European Union, starting at the end of December, about 1.9 million people in Germany, or around 2.2 percent of the population, have received at least one vaccination dose, according to the health authorities there. In the United States, more than 30 million people, or about 7.6 percent of the population, have received at least one shot.

The past few weeks in the United States have been the deadliest of the coronavirus pandemic, and residents in a majority of counties remain at an extremely high risk of contracting the virus. At the same time, transmission seems to be slowing throughout the country, with the number of new average cases 40 percent lower on Jan. 29 than at the U.S. peak three weeks earlier.

Other indicators reinforce the current downward trend in cases. Hospitalizations are down significantly from record highs in early January. The number of tests per day has also decreased, which can obscure the virus’s true toll, but the positivity rate of those tests has also gone down, indicating that the slowed spread is real.

Still, the average reported daily death rate over the past seven days remains above 3,000, compared with less than 1,000 per day in September and October.

Experts say the decrease could mark a turning point in the outbreak after months of ever-higher caseloads. But new, more contagious variants threaten to upend progress and could even send case rates to a new high if they take hold, especially if the national vaccine rollout faces hurdles.

Ten Republican senators are set to meet with President Biden on Monday to push a much smaller alternative to his $1.9 trillion stimulus bill to address the toll of the pandemic, including scaling back another round of direct payments from the government.

The coalition of mostly centrist Republican senators, led by Susan Collins of Maine, on Monday outlined their $618 billion plan, which they are billing as a way for Mr. Biden to pass a pandemic aid bill with bipartisan support and make good on his inauguration pledge to unite the country.

With 10 Republicans on board joining the Senate’s 50 Democrats, a bipartisan bill could overcome the chamber’s 60-vote filibuster rule. But Democrats have shown little enthusiasm for a measure that amounts to less than one third of what the president says is needed to confront the public health and economic crisis.

Still, after receiving a letter from the senators on Sunday requesting a meeting, Mr. Biden called Ms. Collins and invited her and the other signers to the White House, where they are scheduled to meet Monday evening. He also spoke with Speaker Nancy Pelosi of California and Senator Chuck Schumer of New York, the majority leader.

In the hours before the White House meeting, there were indications that some Republicans, including one with close ties to former President Donald J. Trump, supported a bigger relief package to nudge the country to an expected economic recovery later this year.

“If we actually throw away some money right now, so what?” Gov. Jim Justice of West Virginia, who switched parties to support Mr. Trump in 2017, told CNN early Monday.

The proposal by Congressional Republicans is likely to be met with resistance from congressional Democrats, who are preparing this week to begin laying the groundwork for passing Mr. Biden’s plan through a process known as budget reconciliation, which would allow it to bypass a filibuster and pass solely with Democratic votes.

The Republican proposal would include $160 billion for vaccine distribution and development, coronavirus testing and the production of personal protective equipment; $20 billion toward helping schools reopen; more relief for small businesses; and additional aid to individuals. The package would also extend enhanced unemployment benefits of $300 a week — currently slated to lapse in March — until June 30.

“We recognize your calls for unity and want to work in good faith with your administration to meet the health, economic and societal challenges of the Covid crisis,” wrote the Republican group, which includes Senators Lisa Murkowski of Alaska, Bill Cassidy of Louisiana and Mitt Romney of Utah.

The measure omits a federal minimum wage increase Mr. Biden included in his plan. It would also whittle down his proposal to send $1,400 checks to many Americans, and limit it to lower-income earners.

The proposal calls for checks of up to $1,000 for individuals making $50,000 a year or less and families with a combined income of up to $100,000, with individuals earning less than $40,000 — and families earning less than $80,000 — receiving the full amount. Previous rounds of direct payments were targeted to Americans earning less than $99,000 annually, with those earning less than $75,000 receiving the full amount.

“Let’s focus on those who are struggling,” Senator Rob Portman, Republican of Ohio and a member of the group, said Sunday on the CNN program “State of the Union.”

Mr. Biden and Democrats have said they want to work with Republicans, but will press ahead without them if they cannot win agreement on a robust response.

“His first responsibility as president is to help take care of the families who need it,” Senator Elizabeth Warren, Democrat of Massachusetts, said of Mr. Biden on Sunday, telling CNN that he should move ahead with his full plan if Republicans would not agree.

Congress approved more than $4 trillion through a series of bills last year to address the coronavirus crisis and its economic fallout. Most recently, in December, lawmakers passed a $900 billion stimulus plan that included $600 direct checks to many Americans.

That package sprang from a compromise forged by many of the same centrist Republicans who are to meet with Mr. Biden on Monday, who joined moderate Democrats to force their leaders to the negotiating table to find common ground.

The American economy will return to its pre-pandemic size by the middle of this year, even if Congress does not approve any more federal aid for the recovery, but it will be years before everyone thrown off the job by the pandemic is able to return to work, the Congressional Budget Office projected on Monday.

The new projections from the office, which is nonpartisan and issues regular budgetary and economic forecasts, are an improvement from the office’s forecasts last summer. Officials told reporters on Monday that the brightening outlook was a result of large sectors of the economy adapting better and more rapidly to the pandemic than originally expected.

They also reflect increased growth from a $900 billion economic aid package that Congress passed in December, which included $600 direct checks to individuals and more generous unemployment benefits.

The budget office now expects the unemployment rate to fall to 5.3 percent at the end of the year, down from an 8.4 percent projection last July. The economy is expected to grow 3.7 percent for the year, after recording a much smaller contraction in 2020 than the budget office initially expected.

The rosier projections are likely to inject even more debate into the discussions over whether to pass President Biden’s $1.9 trillion economic rescue package. It could embolden Republicans who have pushed Mr. Biden to scale back the plan significantly, saying the economy does not need so much additional federal support and that another big package could “overheat” the economy.

But the report shows little risk that happening. The economy is projected to remain below potential levels until 2025 on its current path. And big economic risks remain. The number of employed Americans will not return to its pre-pandemic levels until 2024, officials predicted, reflecting the prolonged difficulties of shaking off the virus and returning to full levels of economic activity.

The Federal Reserve chair, Jerome H. Powell, warned last week that the economy was “a long way from a full recovery” with millions still out of work and many small businesses facing pressure.

Budget officials said the rebound in growth and employment could be significantly accelerated if public health authorities were able to more rapidly deploy coronavirus vaccines across the population.

As it stands, the budget office sees little evidence of growth running hot enough in the years to come to spur a rapid increase in inflation. It forecast inflation levels below the Federal Reserve’s target of 2 percent for years to come, even with the Fed holding interest rates near zero.

Other independent forecasts, including one from the Brookings Institution last week, have projected that another dose of economic aid — like the $1.9 trillion package Mr. Biden has proposed — would help the economy grow more rapidly, topping its pre-pandemic path by year’s end.

A team of World Health Organization experts investigating the origin of the pandemic has started its mission in the Chinese city of Wuhan by visiting some of the places first hit by the coronavirus.

The team of 15 scientists has in recent days visited a live animal market, a hospital and a disease control center in the city, where the virus emerged in late 2019.

The inquiry will most likely be painstaking, and it could be months or years before the team uncovers answers about how the coronavirus initially spread to humans. Still, the W.H.O. experts say they are gaining important insights on the ground from Chinese scientists during their first visit, which will conclude in mid-February.

“We’ve decided to stay away from theories, because there are so many theories,” Marion Koopmans, a Dutch virologist on the team, said in a telephone interview. “We are trying to look at the data and to build a list of what are possible sources.”

China has tried to use the inquiry to its political benefit, saying that the government is showing transparency by allowing experts into the country.

But the authorities have continued to control the visit of the scientists, forcing them to undergo two weeks of quarantine in Wuhan and setting their itinerary. On Saturday, the experts were taken to a government-run museum celebrating China’s response to the outbreak, before visiting a hospital that treated some of the first people to fall ill with the virus.

The W.H.O. team also visited the Huanan Seafood Wholesale Market in Wuhan. Scientists initially believed the outbreak began at that market — lots of the first cases were linked to it — but many experts now doubt that theory.

The police in China have broken up a counterfeiting ring that they say manufactured and sold more than 3,000 fake coronavirus vaccines across the country, Xinhua, China’s state-run news agency, reported on Monday.

More than 80 suspects have been arrested in the provinces of Jiangsu and Shandong, in the city of Beijing and in other places, Xinhua said.

According to the agency, the police said that the main suspect, a person surnamed Kong, had been injecting saline into vials and selling them as coronavirus vaccines since September.

“The manufacturing and selling of fake vaccines are crimes of a vile nature and can cause serious harm,” Xinhua said. It added that the police were urging members of the public to get vaccinated “through the regular channels to avoid being deceived.”

The arrests began with an order from the Ministry of Public Security to crack down on vaccine-related crimes. Late last year, the demand for Covid-19 vaccines in China was so high that it inspired a cottage industry of scalpers who charged as much as $1,500 for an appointment.

The government is also wary of having to deal with the possible political fallout from another vaccine scandal. In recent years, reports that Chinese companies have fabricated data about their vaccines or made inoculations that have sickened infants have rattled public confidence in domestic vaccines, even though they have been proved safe. Many well-off parents shun them in favor of their Western counterparts.

Unlike many other countries, China has not signaled that it plans to vaccinate its entire population of 1.4 billion people. It has vaccinated about 24 million people, mostly essential workers, about half of its target of inoculating 50 million people by Feb. 12, the start of the Lunar New Year.

During January, the pandemic’s deadliest month, Laredo, Texas, held the bleak distinction of having one of the most severe outbreaks of any city in the United States. The death toll in the overwhelmingly Latino city of 277,000 now stands at more than 630 — including at least 126 in January alone.

When the virus made its way to the borderlands almost a year ago, Dr. Ricardo Cigarroa could have just hunkered down. He could have focused on his profitable cardiology practice, which has 80 employees. He could have kept quiet.

Instead, Dr. Cigarroa has become a top crusader and the de facto authority on the pandemic along this stretch of the U.S.-Mexico border.

On regional television stations, he calmly explains, in both English and Spanish, how the virus is evolving. Known for making Covid-19 house calls around Laredo in his old Toyota Tacoma pickup, he is interviewed so often that Texas Monthly called him “The Dr. Fauci of South Texas,” comparing him to Dr. Anthony S. Fauci, the country’s top infectious disease expert — though Dr. Cigarroa holds no official government portfolio.

Lately, Dr. Cigarroa has been losing his patience.

Looking exhausted in a video posted on Facebook, he blasted political leaders for allowing the virus to rampage through this part of South Texas. Dr. Cigarroa singled out Gov. Greg Abbott, a Republican, for refusing to allow Laredo to impose stricter mitigation measures.

“To the governor: It’s OK to swallow your pride,” Dr. Cigarroa said, stunning some viewers with a warning that the virus could kill 1 in 250 Laredoans by midyear. “It’s OK to say that you’re not going to do it, and then do it to save lives.”

Pleading with the people of Laredo to consider civil disobedience in the form of staying home from work if politicians fail to act, he added, “The only thing that will save lives at this point will be staying home and shutting down the city.”

As Democrats and Republicans spent months last fall arguing over how to rescue the economy, one provision drew widespread support from lawmakers: reviving the Paycheck Protection Program, the government’s marquee effort to help small businesses weather the pandemic.

The Senate Republican leader, Mitch McConnell of Kentucky, called the lending program “a bipartisan slam dunk.” House Democrats included an extension and expansion of the program in aid packages in the summer and the fall. And Treasury economists said in December that the program might have saved nearly 19 million jobs.

Yet there is dissent from one notable contingent: Academic economists who have studied the program have concluded that it has saved relatively few jobs and that, at a cost of more than half a trillion dollars, it has been far less efficient than other government efforts to help the economy.

“A very large chunk of the benefit went to a very small share of the firms, and those were probably the firms least in need,” said David Autor, an M.I.T. economist who led one study.

The divergence in views over the program’s economic payoff stems in part from ambiguity about its goals: saving jobs or saving businesses.

Using different methodology than the Treasury economists, Mr. Autor says the Paycheck Protection Program saved 1.4 million to 3.2 million jobs. Other researchers have offered broadly similar estimates.

Given the program’s cost, saving jobs on that scale doesn’t necessarily qualify as a success. Unemployment benefits also provide income, at far less expense, and programs like food assistance and aid to state and local governments pack a larger economic punch, according to many assessments.

And because the paycheck program was designed to reach as many businesses as possible, much of the money went to companies that were at little risk of laying off workers, or that would have brought them back quickly even without the help.

Many policy experts on Wall Street and in Washington — as well as businesses and banks on Main Streets across the country — say the program’s merits should be assessed instead on what it did to save businesses. On that basis, they say, it helped prevent a greater calamity and fostered economic healing.

This Groundhog Day will not be at all like the others.

As far back as 1900, The New York Times was already referring to this annual “hoary superstition” as a tradition.

Like clockwork, the event draws the curious and worldwide attention. Will a portly groundhog named Punxsutawney Phil see his shadow? The feeling that this may never change was accelerated by a popular 1993 movie starring Bill Murray as a weatherman who is “inexplicably living the same day over and over again” as he covered the annual festivity in Punxsutawney, a bucolic borough in western Pennsylvania about 300 miles west of Midtown Manhattan.

Change does not come easy to this part of the world. Until, that was, the coronavirus pandemic.

The event will proceed on Tuesday in Punxsatawney, but it will be held virtually. The organizers of the event, the Punxsutawney Groundhog Club, said in a recorded message that “No in-person attendance or guests will be allowed on the ground.”

As for the massive snowstorm burying parts of the Northeast, organizers are, for now, forging ahead. Gobbler’s Knob, the groundhog’s home turf, will be closed on Monday at 5 p.m. but will reopen on Tuesday by 9 a.m. The livestream will begin that day at 6:30 a.m.

That dispatch was, itself, a hybrid of modernity and antiquity. It was posted on Instagram. But the words were printed on a sign, held by a man.

Japan’s biggest cities are under a state of emergency as coronavirus deaths rise, even while the country tries to convince the world it can safely hold the Summer Olympics. South Korea is prohibiting gatherings of five or more people to keep a recent surge under control. Hong Kong imposed stringent lockdowns on some of its poorest neighborhoods to stop an uptick.

And yet none of these places have begun to carry out the only solution with any hope of putting the pandemic behind them: vaccinations.

While the United States and most nations in Europe, as well as China and India, have begun inoculating their populations, Japan, South Korea and Hong Kong have stood out by proceeding much more slowly.

Japan will not even begin to vaccinate medical workers until the end of February. The same is true in South Korea, and those over 65 will not start receiving inoculations until May. Hong Kong, a semiautonomous territory of China, will begin vaccinating “high risk” groups in the middle of February.

To a certain extent, the three East Asian economic powerhouses have the luxury of time. Despite recent increases in infections, they have not experienced the kinds of outbreaks that have devastated the United States or Britain.

The delays, which come as more contagious and perhaps deadlier variants of the virus are emerging around the globe, could hamper these governments’ efforts to protect the public and restore normalcy for their weary populations.

But postponement also offers opportunities. The laggards can take the time to learn from the troubled rollouts in the United States and Europe.

By moving more deliberately, the East Asian governments may also be able to alleviate some concerns among the public about the remarkable speed with which the vaccines have been created. In Japan and South Korea, polls show that many people are reluctant to get vaccinated right away.

Supply, too, may restrain the speed of the rollout. While Hong Kong approved Pfizer’s vaccine in January, neither Japan nor South Korea has approved any yet.

In theory, Japan has a more urgent deadline. The government is insisting that it will proceed with the Olympics despite intensifying questions about the feasibility of doing so. The Games, which were originally scheduled for 2020 in Tokyo but postponed to this summer, are scheduled to open on July 23.

The scattered reports from around the country can play like a cruel irony: Someone tests positive for the coronavirus even though they have already received one or both doses of a Covid-19 vaccine.

Notable examples

It’s happened to at least three members of Congress recently:

But it’s been reported in people in other walks of life too, including Rick Pitino, a Hall of Fame basketball coach, and a nurse in California.

How can that happen?

Experts say cases like these are not surprising and do not indicate that there was something wrong with the vaccines or how they were administered. Here is why.

• Vaccines don’t work instantly. It takes a few weeks for the body to build up immunity after receiving a dose. And the vaccines now in use in the U.S., from Pfizer-BioNTech and Moderna, both require a second shot a few weeks after the first to reach full effectiveness.

• Nor do they work retroactively. You can already be infected and not know it when you get the vaccine — even if you recently tested negative. That infection can continue to develop after you get the shot but before its protection fully takes hold, and then show up in a positive test result.

• The vaccines prevent illness, but maybe not infection. Covid vaccines are being authorized based on how well they keep you from getting sick, needing hospitalization and dying. Scientists don’t know yet how effective the vaccines are at preventing the coronavirus from infecting you to begin with, or at keeping you from passing it on to others. (That’s why vaccinated people should keep wearing masks and maintaining social distance.)

• Even the best vaccines aren’t perfect. The efficacy rates for Pfizer-BioNTech and Moderna vaccines are extremely high, but they are not 100 percent. With the virus still spreading out of control in the U.S., some of the millions of recently vaccinated people were bound to get infected in any case.