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May 26, 2020

What we can (and can't) expect from a coronavirus vaccine

Daily Briefing

    People worldwide are anxiously awaiting the creation of an effective vaccine for the new coronavirus, which is being touted as a beacon of hope for ending the Covid-19 pandemic. But experts say the public should be measured in their expectations for the vaccine—and shouldn't expect it to eradicate the virus entirely.

    Will we really have a coronavirus vaccine in 12 to 18 months?

    Vaccines can have setbacks

    For one, experts note that new vaccine candidates can face setbacks in both safety and efficacy—and the risks of those setbacks can increase when development of a vaccine is rushed.

    For example, in 1976, the United States rushed development and approval of a vaccine in response to fears of a swine flu outbreak. The disease wasn't as widespread as initially feared, and the vaccine ultimately led to 450 people developing Guillain-Barré syndrome, a rare neurological disorder[AAL1] .

    Similarly, the polio vaccine can serve as a warning against rushing to quickly manufacture vaccines, Elena Conis, a professor at the University of California, Berkeley and colleagues write in the New York Times. They note that, less than a month after the U.S. government approved a polio vaccine, officials reported six polio cases associated with doses of the vaccine manufactured by the California-based Cutter Laboratories. Investigators found that Cutter didn't completely kill the polio virus in some of the vaccine batches, which ultimately led to more than 200 cases of polio and 11 deaths, Conis and colleagues write.

    Conis and colleagues note that, since the 1950s, when the polio vaccine was first approved, approval and manufacturing safety protocols for drugs have improved significantly. However, they caution that some of these protocols are "being swept aside to speed" the development of a vaccine against the new coronavirus.

    The coronavirus vaccine likely will be similar to the flu vaccine—and not a one-time cure all

    Experts also caution that a vaccine for the new coronavirus isn't likely to be a panacea for stopping the virus. Rather, a coronavirus vaccine likely will be similar to the seasonal flu vaccine, which doesn't protect against all strains of influenza. Instead, the flu vaccine reduces a person's risk of contracting the flu and their risk of developing a severe case of the disease if they do contract it. 

    Marie-Paule Kieny, chair of a committee advising the French government on coronavirus vaccines, explained, "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."

    A recently released preprint study on a coronavirus vaccine candidate being developed by Oxford University and AstraZeneca found that, in macaques, the vaccine protected the primates from developing pneumonia stemming from Covid-19, the disease caused by the new coronavirus. However, the macaques still had high levels of the virus in their upper airways.

    Vincent Munster—chief of the virus ecology unit at the National Institute of Allergy and Infectious Diseases' Rocky Mountain Laboratories, who was a leader on the study of the vaccine candidate in macaques, said he thinks a vaccine that could mitigate the symptoms of Covid-19 would be a significant advancement in the world's fight against the disease. "If we push the disease from pneumonia to a common cold, then I think that's a huge step forward."

    Further, Michael Mina, an infectious disease epidemiologist at Harvard University's T.H. Chan School of Public Health, said experience with other human coronaviruses suggests that any immunity humans potentially develop after infection with the new coronavirus isn't lifelong. Therefore, people shouldn't expect a vaccine against the new coronavirus to provide lifelong immunity, either.

    "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," he said.

    If that's the case, people would need to be vaccinated against the new coronavirus regularly to keep up immunity, like they do for the flu.

    Overall, Kanta Subbarao, a vaccine expert and director of the World Health Organization's influenza collaborating center, said perception of a vaccine against the new coronavirus should be similar to that of a flu vaccine. "I think that will be the messaging, that we're not going to prevent all infection," he said. "We're going to prevent disease."

    Similarly, Munster said, "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."

    The new coronavirus still could be widespread, as Americans may be hesitant to get vaccinated

    In addition, some people might refuse to get the vaccine once it becomes available, which would further hamper efforts to stop the new coronavirus' spread. 

    Findings from a recent poll by Reuters and IPSOS suggested that many Americans may not be interested in getting vaccinated against the new coronavirus. Just under 25% of the poll's respondents said they were either not at all or not very interested in getting the vaccine, and another 11% said they were unsure. In comparison, just under two-thirds of the poll's respondents said they were "very" or "somewhat" interested in getting vaccinated against the new coronavirus.

    William Schaffner, an infectious disease and vaccine expert at Vanderbilt University Medical Center, expressed surprise over the responses. "It's a little lower than I thought it would be with all the attention to Covid-19," he said. "I would have expected somewhere around 75%."

    But Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, said he wasn't shocked by the findings. "It's not surprising a significant percentage of Americans are not going to take the vaccine because of the terrible messaging we've had, the absence of a communication plan around the vaccine, and [a] very aggressive anti-vaccine movement," he said (Conis et. al., New York Times, 5/20; Branswell, STAT News, 5/22; Ax/Steenhuysen, Reuters, 5/21; Axelrod, The Hill, 5/21).

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