Becker's Clinical Quality & Infection Control

10 INFECTION CONTROL Why side effects are more common with 2nd COVID-19 shot: 5 notes By Gabrielle Masson S ide effects appear to be more common aer the second dose for both Pfizer-BioNTech and Moderna COVID-19 vaccines. Both vaccines have received FDA emergency use authorization, and both companies' clinical trials recorded participants experiencing side effects. But why is the second dose more likely to be tied to more side effects? How COVID-19 mRNA vaccines work Both Pfizer and Moderna vaccines are mRNA vaccines, which means they use a copy of a natural chemical — messenger RNA — to pro- duce an immune response. ere are spike proteins on the surface of SARS-CoV-2, the virus that causes COVID-19, which help the virus bind to other cells and replicate. mRNA vaccines work to induce an immune response against the spike protein, primarily through antibodies, so when a virus is detected in the future, it can be fought off more swily, according to e Atlantic. Why some individuals experience side effects after re- ceiving the vaccine Side effects from the vaccine are normal signs the body is building protection against COVID-19, according to the CDC. Sometimes aer vaccination, the process of building immunity can cause symp- toms, though all side effects should go away within a few days. Inflammation as an immune response can result in redness, swelling and tenderness at the injection site, along with broader systemic re- sponses, such as fever, headache, muscle aches, joint pain or fatigue, reported Fox's WNYW. "A number of things happen with regard to inflammation, but it's really a sign that our immune system is recognizing that there's a foreign protein in our body and is preparing to fight it and get rid of it," William Moss, MD, epidemiologist and executive director of the International Vaccine Access Center at Baltimore-based Johns Hopkins University, told WNYW. e mRNA itself may provoke a reaction from the immune system. "All of a sudden, you have a lot of new RNA that the cell didn't make," Donna Farber, PhD, an immunologist at New York City-based Co- lumbia University, told e Atlantic. Why some people experience more severe side effects after the second dose e Moderna and Pfizer vaccines are administered in two doses, spaced apart by about 28 and 21 days, respectively. More users of V-safe, the CDC's tool to report vaccine side effects, reported side effects within a week of getting their second shot compared to the first, according to a Jan. 27 CDC update. When hit with the second injection, the immune system is already primed. "By the second vaccine, it's already amped up and ready to go," Jas- mine Marcelin, MD, an infectious disease physician at Omaha-based University of Nebraska Medical Center, told e Atlantic. Cells that make antibodies need several days to study the spike's features before they can respond. But by the second dose, adaptive cells are faster to react. "Basically, that second dose is saying, 'Hey, I know a month ago you saw this spike protein. I'm going to remind you once more what it looks like so that you're really ready to attack it,'" Dr. Moss told WNYW. Why the second COVID-19 dose is important While there is some protection from a single COVID-19 vaccine dose, protection may be shorter, though it remains unclear. Extend- ing the length of time between doses or skipping the second shot would be "premature and not rooted solidly in the available evi- dence," the FDA said Jan. 4. e agency emphasized the importance of continuing the two-dose regimen at the studied intervals. Vaccinated individuals who aren't experiencing any side effects People shouldn't be concerned by a lack of vaccine side effects, either. "People who don't have moderate or severe side effects from the vaccine can still have a very protective immune response. ey just didn't have, for various reasons, that intense inflammatory response," Dr. Moss told WNYW, citing a combination of genetics and prior history of exposure. n CDC: Tight-fitting masks, two masks maximize protection against infectious aerosols By Erica Carbajal D ouble masking or knotting and tucking a single medical procedure mask helps prevent air leakage and improve mask performance, according to the CDC's Feb. 10 Morbidity and Mortality Weekly Report. After performing lab experiments with dummies, the CDC found that modifying masks to tighten the fit re- duced exposure to potentially infectious aerosols, includ- ing those in the size range able to transmit SARS-CoV-2, by about 95 percent. Researchers evaluated two modifications: layering a cloth mask over a medical procedure mask, known as double masking, and a single medical procedure mask with knot- ted ear loops and tucked-in sides to help get rid of any loose material. When the infected wearer (source) and receiver were both fitted with the double mask or knotted and tucked mask modifications, the cumulative exposure of the receiver was reduced by 96.4 percent and 95.9 percent for each modification, respectively. The report also highlighted the use of solid or elastic mask fitters and a modification where a nylon cover is placed over a mask, as additional effective options to improve mask fit. n

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