For many Americans chafing to return to normalcy, recent reports that at least two experimental covid-19 vaccines are highly effective come as welcome news in the midst of a frightening surge of infections and deaths. The first shots may be given in mid- to late December, but that doesn’t mean you can hug your friends, stop washing your hands or throw away your mask any time soon.

The return to many of our old familiar ways will take time, and how much time remains unclear. The answers await more research into the vaccines, how they can be distributed and how many people are willing to get them.

"A vaccine won't be available immediately for everybody," says Arthur Reingold, a professor of epidemiology at the School of Public Health at the University of California, Berkeley. He also chairs California's COVID-19 Scientific Safety Review Workgroup, which will evaluate the safety and efficacy of covid-19 vaccines.

“It probably will take four to six months,” he says. “What that says to me is that people will have to keep wearing masks at least until spring. We won’t be in a magically different situation by February or March. I don’t see how that can possibly happen.”

Equally important are the unknowns about the vaccines themselves. Scientists still don’t know how long vaccine-induced protection will last, for example, or whether inoculations can block actual infection, or only prevent the onset of disease. If the latter turns out to be the case, meaning the vaccines keep us from getting sick, but not infected, we still could be infectious to others. Until we know, don’t toss those masks into the trash.

“The bottom line is that although an effective vaccine will certainly diminish greatly the relative risk of transmission, we still should not completely abandon basic public health measures, including the wearing of masks,” Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said in an email.

In a recent JAMA report, he and his colleagues stressed the need for continued vigilance, saying such precautions as mask-wearing would be “essential” during any initial vaccine rollout.

Robert T. Schooley, an infectious diseases specialist at the University of California, San Diego, points out that although vaccines will provide another level of protection, the virus will not disappear and will be around for many years.

“But until we know more about how long protection lasts and the extent to which people are protected,” he says, “it’s important to continue to use all the tools we have to keep the virus in check, and that means masks, social distancing and ventilation.”

These safeguards will ensure against transmission if the vaccines fail to prevent infection, says William Schaffner, professor of preventive medicine at Vanderbilt University. He urges people to be patient.

“The average person wants answers yesterday,” he says. “But try to keep in mind that we are still moving at rocket speed.”

Next summer

Some experts say they hope for a level of protection by next summer that will allow us to resume certain activities. “I’m not sure about mass gatherings, such as baseball games, but it is plausible,’’ Reingold says. “Time will tell.”

Andrew Badley, an immunovirologist who chairs Mayo Clinic’s covid-19 task force, says the return of any normal activities depends on numerous factors, including how many people get vaccinated.

“The only possibility that life will return to normal by summer is if the majority of the population receives the vaccines by then and the early efficacy data is borne out in ongoing studies,” he says. He adds, however: “I think it is unlikely we will be able to vaccinate the majority of the population by then.”

Schaffner expects a “substantial improvement” by summer, although probably not a complete return to our former lives. But he adds: “Next Thanksgiving could well be back to near-normal.”

The two leading vaccine candidates were developed by Moderna Therapeutics, which reported 94.5 percent efficacy, and Pfizer partnering with the German company BioNTech, which demonstrated a 95 percent success rate, including 94 percent among those 65 and older.

Both vaccines involve a new and promising technique based on messenger RNA, or messenger ribonucleic acid (mRNA), that use a synthetic form of RNA to trick human cells into making the virus’s distinctive “spike” protein, prompting the immune system to generate antibodies in response.

Preliminary findings about their efficacy were based on the number of people who became ill, not on whether the vaccines prevented infection.

“Although [preventing infection] might be the ultimate effect, we do not know that at this point,” says Fauci, the nation’s most recognized expert on the pandemic. “The primary endpoint [in these studies] was the prevention of symptomatic infection. So it is conceivable that the vaccine would protect you against clinical disease, but not necessarily protect you against infection.”

Schooley expects that further research will study participants’ blood to see whether their antibodies are a response to the vaccine or to a natural infection with the virus, or both.

The vaccines generate antibodies to a single viral protein — the “spike” — while natural infection produces antibodies to multiple viral proteins.

“If you find somebody with antibodies to the spike protein alone, it means they came from the vaccine,’’ he explains. “If they have that, plus other viral antibodies, they may have been vaccinated — but they also have been infected,” he says. “That will tell us whether the vaccine, in addition to reducing disease, also reduces infection. Also, we still don’t know the durability yet,” referring to how long protection will last “or the level of protection of different subgroups of people at risk,” such as the elderly or those with underlying medical conditions.

Vaccinations will probably come in waves, with initial inoculations expected before the end of the year, with front-line health-care workers and emergency responders receiving the first doses, followed by the most vulnerable, including the elderly, especially those in nursing homes, and people with underlying medical conditions, and then younger, healthier people. Participants in the trials who received a placebo may also be offered the vaccine early. Those who have been sickened and recovered from covid-19 probably will also receive vaccinations, since it’s still unclear how long natural immunity will last — although they probably will come at the end of the line, experts say.

Two shots are required, each one month apart. Because it is still unclear how long protection will last, public health officials don’t know whether boosters will be necessary, and, if so, how frequently.

Patience may be tough for many Americans who long to see their children and grandchildren and are exhausted by fear and the effort to cope with the pandemic. I told Fauci of a recent telephone conversation I had with my adult son who — although he understands the necessity for distance — is unhappy we can’t see and hug each other right now. Fauci offered both caution and hope, saying the danger could drop considerably once both of us are vaccinated.

“Since all risks are relative, I would think that if you are vaccinated with a 95 percent effective vaccine and your son is also vaccinated, the relative risk of you or your son getting infected or infecting one another would be so low, [although] not zero, that you could feel relatively comfortable in hugging your son,” he says. “It is likely that you also could start doing things that you did not do before,” meaning the ability to enjoy other social activities that have been restricted.

Optimism about vaccine

Microbiologist Peter Palese, an expert in RNA viruses who chairs the department of microbiology at Mount Sinai’s Icahn School of Medicine, is optimistic these vaccines will prove effective against both infection and disease. He and his wife both volunteered for the Pfizer study and, while he received a medically worthless placebo, she got the real thing, he discovered.

Palese says she produced many times higher levels of antibodies than their 48-year-old physician son who contracted the disease and recovered. He is enthusiastic about the new approach, saying it will transform the development of future vaccines as well as the current pandemic. (Palese said Pfizer did not tell him or his wife whether they had gotten the vaccine or the placebo. “I work in the area of covid-19,” he said, “so I know a little bit about the tests.”)

“Messenger RNA is extraordinary,” Palese says. “It’s an unbelievable breakthrough that will change the face of this plague.”

Others are more cautious.

“The biggest danger is that people will think we are done with this, but we are dealing with two studies with the first two months of results, when vaccines look their best,” Schooley says. “There may be some loss of protection over time, and people need to pay attention to them over the long term.”

But even if the vaccines prove fully effective, they won’t do much to curb the spread of infection and disease if people refuse to get the shots.

Polls suggest that 40 percent or more of Americans will not get a covid-19 vaccine, a statistic that greatly worries public health officials about the prospects of developing herd immunity. This results after a vast majority of the population has achieved protection, giving the virus many fewer people to infect, thus reducing transmission and illness.

Still, it’s also uncertain what we need in terms of vaccine coverage for that to happen.

“We do not yet know if we need to vaccinate 50 percent or 90 percent of the population in order to see a positive impact of the vaccines on community transmission,” Badley says.

“There is a lot of vaccine hesitancy,” Reingold says. “There is a spectrum in this country regarding attitudes toward vaccination. The world doesn’t divide neatly into yes or no. It’s much more complicated. There are people who are skeptical about what we know about these vaccines right now, and would rather wait and stay home and take their chances. There also are many who are amenable to being vaccinated eventually. And there are others at the end of the spectrum who say: never.”

Fauci says the faster the country reaches herd immunity, the faster everyone’s lives will return to normal.

“Regarding society opening again, economically and otherwise, this will depend on the uptake of the vaccine,” Fauci says. “Even with a highly effective vaccine, if only half the population gets vaccinated, the protection at the community level would not be adequate and certainly not optimal.”

In short, life in a post-vaccine world remains a complicated scenario for now.

“It may be, as more people get vaccinated, the risk of getting infected becomes lower,” Schooley says. “People who are at risk of dying if they get infected may want to wear a mask for a really long time — remember, people who are older and have underlying conditions, and are at the greatest risk for getting sick — may be least likely to robustly respond to the vaccine. We will learn more as more data come out. Certainly the more people who become vaccinated, the better.”

Badley is optimistic that an increasing number of people will roll up their sleeves once researchers learn more about the vaccines’ safety and efficacy, and successfully convey that information to the public.

“Smallpox is the only infectious disease eradicated by a vaccine, and it took almost 200 years from the time the disease was discovered,” he says. “We’ve come a stunningly long way in a short period of time and, if the trajectory continues, we should have good control over the pandemic in the upcoming months and years.”

Clarification: An earlier version of this story incorrectly implied that Pfizer may have revealed to Peter Palese that he had received a placebo as part of its vaccine trial. In fact, Palese’s own investigations indicated to him that he had been given the placebo. The story has been revised.