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Microbiology and immunology professors explain the COVID-19 vaccine and what sets it apart from past vaccines
On Dec. 11, 2020, the Pfizer-BioNTech vaccine was approved for use by the Food and Drug Administration (FDA) after a series of experimental trials since mid-March. The Moderna vaccine also received emergency authorization from the FDA on Dec. 18, 2020. Barbara Shacklett, a professor at the UC Davis School of Medicine whose research focuses on cell-mediated immune responses to HIV, noted that although the vaccine hasn’t taken long to be approved, the experimental process wasn’t carried out hastily.
“Even though the vaccine has become available in record time, it nevertheless went through extensive testing in clinical trials to determine that it was both safe and effective,” Shacklett said via email. “The process was accelerated in this case because of the urgency of the situation, but that doesn’t mean important steps were skipped or overlooked.”
Dr. Stefan Rothenburg, an associate professor in the School of Medicine’s department of medical microbiology and immunology, emphasized that no serious symptoms have been linked to the vaccine.
“I think the short term safety profiles are very encouraging,” Rothenburg said. “There have been very few serious side effects—you cannot really call it side effects—but very few instances where some of the participants in the trials had some disease. But it has been concluded by the expert panel that this had nothing to do with the vaccine.”
According to Rothenburg, some of the trial participants who experienced symptoms were part of a placebo group.
“In the placebo groups they had some cases where people developed some health issues,” Rothenburg said. “And this is just kind of normal. If you have a large number of participants, some people, in a random fashion, will always develop some health issues.”
Vaccines use a form of antigen that the immune system recognizes and responds to. According to Shacklett, vaccines can be made up of weakened strains of a virus, lifeless virus particles or a small piece of the virus particle—usually a protein. The Pfizer-BioNTech vaccine employs the last method; however, the genetic information called messenger RNA (mRNA) is used instead of a protein. The Pfizer-BioNTech vaccine is the first mRNA vaccine to be approved for general use.
“The vaccine contains a very small piece of the SARS-CoV2 virus’ RNA,” Shacklett said. “Once it’s in a person’s body, this RNA serves as a template so that the person’s cells can produce a single, strongly immunogenic protein from the virus, the ‘spike’ protein. Importantly, this small piece of RNA doesn’t contain nearly enough information to produce the whole virus.”
Shacklett stated that after the body uses the mRNA, it’s discarded.
“Once the vaccine material is taken up by our body’s cells, it is ‘read’ by the cellular machinery that makes proteins, but afterwards it is completely broken down and lost,” Shacklett said. “The mRNA does not become stably integrated into our cells; instead, after it is used as a template, it’s destroyed by enzymes inside our cells.”
Rothenburg mentioned that the majority of Americans are leaning toward becoming vaccinated.
“Right now it seems that at least 80% of the population in the U.S. have a positive view of the [COVID-19] vaccines,” Rothenburg said. “So I think about 40% would take it right away. Another 40% want to wait a little bit, but it’s generally a positive and this is definitely encouraging.”
According to Rothenburg, the virus won’t be able to be transmitted if a certain threshold is reached in the number of vaccinated individuals.
“If we get a vaccination coverage of between 70 and 80%, we are at the stage where the virus would have problems to get transmitted, basically because people are more immune,” Rothenburg said.
Dr. Jose Torres, a professor in the department of medical microbiology and immunology whose research focuses include viral immunology, stated that the vaccine will likely offer immunity for months.
“A few months of protection (three to six) is a reasonable expectation until we gather results from a large number of vaccinees,” Torres stated in an email. “The real long-term efficacy can only be determined a few years after widespread vaccine introduction.”
Both the Pfizer and Moderna vaccines have proven to have a more than 90% success rate.
“Many scientists that are experts in this field are very surprised with the
exceptionally high early protection levels reported by the companies that developed the final
versions of these new types of vaccines,” Torres said. “Time will tell if this becomes a safe and reliable technology for inducing long-term protection and memory.”
Written by: Lyra Farrell — firstname.lastname@example.org