The Science Behind COVID-19 Vaccines

Clockwise from top left: Cynthia Leifer, Gary Koretzky, Avery August and Deborah Fowell. Credit: Jason Koski / Cornell University

COVID-19 vaccines, which have been proven to be extremely safe, are effective at protecting the public in two ways: they protect most people from getting sick; and they reduce the chance that people will pass the virus on to others.

This was one of the key messages conveyed during “The Science Behind COVID-19 Vaccines,” a Q&A-style virtual panel discussion on April 12 with Cornell immunology experts who addressed frequently asked questions from the Cornell community and others about vaccines. answered.

The morning after the event, the Centers for Disease Control and the Food and Drug Administration (FDA) released a joint statement reporting that although 6.8 million doses of the Johnson & Johnson (J&J) vaccine have been administered in a single dose, the federal agencies were. reviewing data on six reported US cases of a rare and serious type of blood clot in subjects who received the J&J vaccine. All six cases occurred in women between the ages of 18 and 48, and symptoms occurred between 6 and 13 days after vaccination, the statement said. The agencies recommended a break from the use of this vaccine.

“We didn’t know this information yesterday,” said Cynthia Leifer, professor in the Department of Microbiology and Immunology at the College of Veterinary Medicine, and moderator and speaker at the panel discussion. “Clinical trials have failed to detect these rare events. But even after FDA approval through emergency use authorizations of the COVID-19 vaccines, the scientific community has continued its rigorous evaluation of the new vaccines. The pause announced today is a reflection of the caution we are taking to ensure safety. She added that patience is required as scientists investigate and gather more information to better understand how these rare side effects may be related to vaccines.

“The fact that we were able to detect this problem and discontinue use of the vaccine shows that the ongoing safety analysis is working to detect these types of events as early as possible,” she said.

In the discussion, panelist Deborah Fowell, professor and chair of the Department of Microbiology and Immunology, gave a brief overview of how the vaccines work. Vaccines, she said, contain “a small portion of the virus, or a protein from that virus, or the machinery to make that protein in our own bodies.” Once introduced, vaccines activate the immune system to create a memory of these elements of the virus, so inoculated people who encounter the virus again respond quickly and are protected from getting sick, Fowell said.

Fundamental research in recent years has enabled immunologists to rapidly develop COVID-19 vaccines, said panelist Avery August, professor in the Department of Microbiology and Immunology, professor at Howard Hughes Medical Institute and vice-provost for academic affairs.

Under normal circumstances, vaccines take years to develop, but scientists used prior knowledge to develop safe and effective vaccines in just under a year, starting all necessary steps simultaneously – including animal testing, two phases of human clinical trials, and manufacturing.

“We basically thrown everything at the vaccine,” said August, adding that COVID-19 vaccines were held to the same rigorous standards as vaccines made under normal timeframes.

All three vaccines approved for use in the U.S. – the two-dose Pfizer and Moderna vaccines and the single-dose paused J&J vaccine – significantly hit the initial 50% efficacy bar set by the government exceeded, said Gary Koretzky, vice-provost for academics. integration, professor in the department of medicine at Weill Cornell Medicine, and adjunct professor in the department of microbiology and immunology.

Most importantly, the vaccines are nearly 100% effective in preventing death and serious complications from COVID-19, Koretzky said. “We learn that when people are vaccinated, not only are they protected from getting the disease itself, but they are also protected from contracting the virus and then giving it to others … not 100% [of the time], but really really good. That’s the key to stopping the pandemic, as asymptomatic transmission is one of the most serious problems with this particular virus, Koretzky noted.

He also said the vaccines are now known to provide immunity for at least 180 days. As time goes on, researchers will learn more about the duration of immunity and whether people need booster shots.

Still, the vaccines have limitations: while nearly 100% effective in preventing serious complications, it is not 100%; and the virus may mutate within infected humans and create variants against which vaccines do not protect. So far, current vaccines have proven to be protective against most circulating variants, August said, but the possibility of new variants emerging for which the vaccine is less protective remains.

For this reason, public health workers are trying to vaccinate people quickly to stay ahead of variants. Since nearly 80% of the public becomes immune, either through vaccination or recovery from COVID-19, we will approach herd or community immunity, Leifer said. That will indirectly protect individuals who cannot receive a vaccine because they are immunocompromised or have allergic reactions.

Vaccinated people have yet to adhere to guidelines for social distance, hand washing and wearing masks, Leifer said.

Many people have reported persistent symptoms after contracting COVID-19, but anecdotal evidence has increasingly shown that vaccination reduces symptoms in some so-called “ long-range jets, ” an encouraging sign now being studied, Koretzky said. “The jury is still out, but that would be a big advantage of these vaccines.”

Despite the positive results, many people remain reluctant to get vaccinated, Leifer said. When discussing reasons for getting vaccinated, the first step is to just listen, she said.

“This virus entered the human population while no person on this Earth was protected, and it spread like wildfire,” she said. In flu, most people have some immunity to vaccines or previous infections, which provides a basic level of protection for the population. COVID-19 also strikes people more seriously and kills more than the flu.

“The only way to get back to a new normal, whatever that will be, is to get as many people vaccinated as possible,” said Leifer.