With a little luck and a lot of science, the world might in the not-too-distant future get vaccines against Covid-19. But those vaccines won’t necessarily prevent all or even most infections.

In the public imagination, vaccines are often seen effectively as cure-alls, like inoculations against measles.

Rather than those vaccines, however, the Covid-19 vaccines in development may be more like those that protect against influenza — reducing the risk of contracting the disease, and of experiencing severe symptoms should infection occur, a number of experts told STAT.


“We all recognize that flu vaccine, in a year when it’s efficacious, you have what, 50% protection? And in a year when it’s poor you have 30% or less than that — and still we use that,” said Marie-Paule Kieny, who is chairing a committee advising the French government on vaccines to prevent Covid-19.

Ideally, vaccines would prevent infection entirely, inducing what’s known as “sterilizing immunity.” But early work on some of the vaccine candidates suggests they may not stop infection in the upper respiratory tract — and they may not stop an infected person from spreading virus by coughing or speaking.


A recently released study in which macaques were vaccinated with one vaccine candidate — this one being developed by Oxford University and AstraZeneca — showed the primates were protected from Covid-induced pneumonia. But the macaques still had high levels of virus replicating in their upper airways. (The paper was a pre-print, meaning it hasn’t yet been peer-reviewed and published in a journal.)

Vincent Munster, who leads the team that conducted that study, said a vaccine that could mitigate the severity of the Covid-19 pandemic would still be a significant contribution in a world struggling to co-exist with a dangerous new virus.

“If we push the disease from pneumonia to a common cold, then I think that’s a huge step forward,” said Munster, chief of the virus ecology unit at the National Institute of Allergy and Infectious Diseases’ Rocky Mountain Laboratories in Hamilton, Mont.

The rush to develop vaccines means that ideal solutions may be out of reach in the immediate term; Munster said he anticipates seeing second-generation vaccines that could be more protective. Other scientists, though, are cautious about how much the world can expect from vaccines against this pathogen.

Michael Mina, an infectious diseases epidemiologist at Harvard’s T.H. Chan School of Public Health, thinks achieving sterilizing immunity with a vaccine will not be possible for Covid-19. Experience with human coronaviruses — and with multiple pathogens that cause colds — shows immunity that develops after infection with respiratory tract infections is not lifelong. In some cases, the duration is measured in months, not years.

“If [infection with] natural coronaviruses doesn’t do it, I don’t think that we should necessarily expect or have the anticipation that we’ll be able to get there with the vaccine,” said Mina, who is also associate medical director of clinical microbiology at Boston’s Brigham and Women’s Hospital.

Munster agreed trying to develop vaccines that confer sterilizing immunity would be a heavy lift with this coronavirus. “I think we really need to focus on what are the fastest achievable true public health goals of the vaccine, which is protecting the vulnerable people against pneumonia and protecting health care workers as well,” he said.

Earlier this week Moderna, the Cambridge, Mass.-based biotech, said eight people in a Phase 1 trial of its Covid-19 vaccine developed neutralizing antibodies to the virus.

Neutralizing antibodies should protect against severe Covid-19 disease, Kanta Subbarao, a vaccine expert who is director of the World Health Organization’s influenza collaborating center in Melbourne, Australia, recently wrote in a commentary in the journal Cell Host and Microbe.

But Subbarao told STAT she wouldn’t be surprised if neutralizing antibodies don’t protect against infection in the upper airways. Like Munster, she doesn’t think that’s reason not to pursue these vaccines.

“Converting this infection to a upper respiratory illness would be, I think, quite a lot better than where we are today,” said Subbarao, who worked on vaccines for SARS, a closely related coronavirus that caused an international outbreak in 2003.

Subbarao said setting public expectations of what these vaccines will be able to achieve is critical.

It would not be helpful if the type of perception that exists about flu vaccines — that they don’t work very well — sets in with Covid-19 vaccines. People don’t credit flu vaccines for what they prevent; they deride flu shots for not protecting them on the occasions when they contract influenza, even though they have been vaccinated.

“We can’t leave all that messaging until we know how good the vaccines are,” Subbarao said. “I think that will be the messaging, that we’re not going to prevent all infection. We’re going to prevent disease.”

The fact that the macaques that Munster’s group vaccinated and then infected had virus in their upper airways was viewed with dismay by some. But Munster noted the animals were infected with large doses of virus; whether the same will be true in people remains to be seen.

Some experts hope that even if the vaccines don’t prevent infection in the upper airways, they may reduce the amount of virus a vaccinated person generates and emits.

“Hopefully it would diminish — although we don’t know this — the levels of replication on the mucosal surfaces,” said Mark Feinberg, CEO of the International AIDS Vaccine Initiative, which is working to develop an orally administered Covid-19 vaccine. That route of administration may improve the vaccine’s capacity to protect the mucus membranes of the upper airways.

Mina sees a potential upside to Covid-19 vaccines that don’t stop infection and transmission, saying low-level circulation of the virus could act as a natural “booster” to keep people’s immunity levels high.

“Then you don’t necessarily have to keep going and getting a vaccine every year, for example. You could rely on some level of natural exposure as long as all the people who are at particular risk have been given the opportunity to be vaccinated as well,” he said.

But there’s the rub, warned Sarah Fortune, chair of the department of immunology and infectious diseases at Harvard’s School of Public Health.

“It’s a little bit sobering to see that, while we may get protection against disease [and] protect people from getting sick, we may not get nearly as effective protection against transmission,” Fortune said during a briefing Thursday for reporters. “Which means that to protect the population, we’re going to have to be vaccinating many, many more people, because we can’t rely on getting to a lot of people and having the epidemic die out through herd effects.”

Andrew Joseph contributed reporting.

  • Sounds good to me! If I can get a shot that makes it so I get a scratchy throat for a week instead of multi-organ failure, I don’t see the problem. Meanwhile, it would buy the front line docs/nurses the time and resources they need to treat the stubborn anti-vaxxers in the ICU and researchers will be able to take all the time they need to develop even better treatments and vaccines. Where do I sign up? Rolling up my sleeve as I type this.

  • The gist of this article is horrible. The new coronavirus is much more than just any flu virus we know. Covid-19 is much more complicated and serious, leads not only to pneumonia, but lung damages, blood clotting, heart failures, Kawasaki disease symptoms, long-lasting exhaustion, and who knows what else yet unknown. To expect to settle for just another flu-shot type of weak in-effective vaccine is utterly unacceptable. If STAT gets that notion from experts, STAT needs to challenge them for bigger and better. It may take longer, but it must be done. Various R&D companies are approaching the virus mechanism from different angles. Moderna’s is a scandalously corruption-laced abused over-hype (there will be class action lawsuits). It will be reputable trustworthy companies like Inovio, Dynavax, Vaxart, Roche, Novavax, Sinovax, Sanofi a.o. – that will deliver a vaccine, or combination, that will work. Prior immunization history must be researched – for Covid resistance, positive or negative links to Covid severity and outcomes. Surely any experts settling for less (like in this article) are doing sub-standard work.

  • Someone should tell this to JB Pritzker.

    He’s made his entire Illinois Recovery plan contingent upon a vaccine. But we don’t know when, or even if, a vaccine will be available, to say nothing of how many years it will be before an effective vaccine has been widely distributed throughout the population. Meanwhile, more and more shops close their doors forever, more and more people go on unemployment, and more and more people mental health issues that manifest in things like increased suicide rates, an increased number of cases of domestic abuse, etc.

    Once upon a time, we had a saying that unemployment equals death. I don’t hear anyone saying that anymore, for some reason.

  • I agree that scientifically that a 100% solve would be great but may be hard to achieve. However, doesn’t a vaccine that mostly eliminates the severe cases effectively allow us to return to pre-COVID-19 days? We will always have colds and flus – the severity of this, and the potential for hospital overload are what makes it most scary. I feel like this point is unfairly underplayed in the article. The concern is not another upper respiratory infection – it’s the choice between keeping society closed or catching a deadly germ. If you solve the severity piece, you have functionally almost won.

  • Thank you for the information provided in this article, that infectious diseases are costly affect both individuals as well as whole societies. May be studies related to analyse there pre and post effects are crucial to define strategies and polycies.

  • I just want something that will let me visit my elderly mom without killing her.

  • Maybe?
    We’ve never developed a single vaccine for any coronavirus, after nearly a century of work on the most common—the common cold.

    The most likely scenario is that we’re going to see every human infected, and live with the virus or its descendants for decades.

    Prepare to see a dead representation of the definition of “decimate.”

    • Charles, I share your uncertainty about a COVID-19 vaccine (although for different reasons than what you mention), but where are you getting this idea from about how COVID-19 is somehow going to infect 100% of the population?

  • It’s wrong to compare SARS-Cov-2 with influenza virus. Influenza has a segmented genome, meaning its different RNA segments can recombine to form new variations, this is called genetic shift, it is the reason why influenza vaccine developers need to predict which variations would be likely and make vaccines for each and every coming season. If prediction is incorrect, then the efficacy is much weaker. On the other hand, SARS2 virus has a single RNA genome, there is no chance for genome recombination like in influenza virus, only random mutations like other common cold coronaviruses, therefore, vaccine will work much better.

    There are over 5 millions confirmed cases, not a single scientifically confirmed case of recovered patients who are infected again.

    Vaccine will work, this is a conclusion based on modern science and medicine. The real question is how long the immunity will last.

    Jack, PhD

    • Thank Jack, I’m a layperson but I was going to make the same comment.

      Also, in terms of perception the Covid vaccine will be different than the “flu shot” – many different pathogens circulate in winter and are lumped in categorically in peoples’ minds as “the flu”. So the flu shot doesn’t seem to work for a lot of people, but the reality is they’re facing bacterial or other respiratory infections. Thus the flu shot only partially achieves the goal of not getting sick in winter.

      Everybody that gets a Covid vaccine will be hoping to fight life-threatening infection from one single pathogen with much higher lethality than other circulating bugs. It sounds like these vaccine candidates will achieve that goal – eliminating the fatal threat. We’re all going to continue getting respiratory infections going forward, but the lethal threat from SARS2 will be gone. So from the “user perspective” the vaccine is indeed very effective.

  • I am a Registered Nurse (retired) with a real interest in science. That is why I have read every article about vaccines for covid 19. In this article written by you, if you had done further research, you would have found out that a unique coronavirus vaccine being developed by the MIGAL group in Israel induces antibody production in three different tissues of the body–including the blood stream and mucosa of the throat. I find this vaccine to be the most exciting one in the pipeline, but one that is seldom mentioned in the media. Their coronavirus vaccine is based upon their already developed coronavirus vaccine for IBV, or avian infectious bronchitis virus. Please read up on MIGAL and then write another article.

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