Becker's Clinical Quality & Infection Control

12 INFECTION CONTROL CDC: mRNA vaccines reduce infection by 90% among healthcare workers By Erica Carbajal T he messenger RNA vaccines from Pfizer-BioNTech and Moder- na were 90 percent effective at preventing COVID-19 infections in re- al-world settings, according to the CDC's Morbidity and Mortality Weekly Report published March 29. Researchers evaluated the efficacy of the vaccines among 3,950 healthcare personnel, first responders and other essential workers who did not have a previous confirmed COVID-19 case. e majority of partici- pants in the study were fully vaccinated, or received both vaccine doses, and 477 received a single dose. Between Dec. 14, 2020, and March 12, 2021, participants self-collected nasal swabs and were tested weekly for COVID-19, regardless of whether they were experiencing symptoms. Findings showed the risk of infection was cut by 90 percent two or more weeks aer receiv- ing the second shot. A single dose was linked to an 80 percent reduced risk of infection at least two weeks aer it was administered. A total of 205 people, or 5.2 percent, tested positive during the study period. Of those infections, 58 percent were identified through testing before the person knew they were infected or experienced symptoms — an indicator that the vaccines are effective at reducing the risk of asymptomatic infection, the CDC said. "ese findings indicate that authorized mRNA COVID-19 vaccines are effective for preventing SARS-CoV-2 infection, regardless of symptom status, among working-age adults in real-world conditions," the report said. n Physician viewpoint: Herd immunity may be closer than you think By Mackenzie Bean M uch of the national dialogue on COVID-19 herd immunity empha- sizes vaccine-based protection and suggests the country is far from achieving this target. However, herd immunity may be closer than some top health officials think when natural immunity is considered, a Johns Hopkins physician wrote in a March 24 op-ed for The Wall Street Journal. Marty Makary, MD, is a surgical oncologist and professor at the Johns Hop- kins School of Medicine and Bloomberg School of Public Health in Balti- more. He said undercounting or ignoring natural immunity from any herd immunity tally is "a scientific error of omission." "Many physicians believe that vaccinated immunity will prove more durable than natural immunity. I agree, and I think everyone should get vaccinated," Dr. Makary said. "But after a year of millions of COVID-19 cases in the U.S., it's clear that reinfections are rare. Natural immunity is real and shouldn't be ignored." Dr. Makary said some health experts point to a lack of data as one of the rea- sons they don't account for natural immunity in their projections. He argued that the National Institutes of Health and CDC should spend more funding investigating this question. "If we say we're going to follow the science, then we need to be willing to consider all the data," he concluded. n 5 reasons COVID-19 herd immunity is likely impossible: Nature By Gabrielle Masson T he idea of gaining "herd immunity" against COVID-19, meaning enough people will eventually be immune to SARS-CoV-2 to stop it from spreading, is starting to look unlikely, according to an article published March 18 in Nature. "We're moving away from the idea that we'll hit the herd-immunity threshold and then the pandemic will go away for good," said epidemiologist Lau- ren Ancel Meyers, PhD, mathematical biologist and executive director of the University of Texas at Austin COVID-19 Modeling Consortium. "The vaccine will mean that the virus will start to dissipate on its own," Dr. Meyers said, but as new variants arise and immunity from infections poten- tially wanes, "we may find ourselves months or a year down the road still battling the threat, and having to deal with future surges." Here are five reasons why scientists are contemplating a new normal that doesn't include herd immunity: 1. It's unclear whether vaccines prevent transmission. 2. Vaccine rollout is uneven. 3. New variants change the herd-immunity equation. 4. Immunity might not last forever. 5. Vaccines might change human behavior. n

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