With millions of Americans getting vaccinated for COVID-19 and new infections and deaths down across much of the United States, it can seem for many people like the pandemic is practically over. This sense has been supported by the lifting of mask requirements for many activities, such as grocery shopping or large outdoor gatherings, in some areas of the country. But a new study modeling the spread of COVID-19 under several possible scenarios, published in the journal JAMA Network Open, shows that even as vaccinations continue, masks and physical distancing have an important role to play in reducing new infections.
Researchers at several universities, most of them in North Carolina, created their model based on past trends in the spread of COVID-19 and current information about how easily the viral infection is transmitted. The model looked at several possible scenarios in North Carolina, including different rates of total vaccination, different levels of vaccine efficacy against the virus (since current or future variants of the virus may escape the vaccine’s defenses in many people), and measures other than vaccination to stop the spread of the virus, such as mask wearing, physical distancing, and school closures. All of these inputs were used to estimate what effect they would have on new infections, hospitalizations, and deaths from COVID-19.
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Masks, social distancing to reduce COVID-19 spread
The researchers found that overall, measures like mask wearing and restrictions on movement or gatherings could still have a substantial impact on COVID-19 hospitalizations and deaths while vaccinations proceed. In the model’s worst-case vaccination scenario — vaccines being 50% effective against the virus, with only 25% of the state population fully vaccinated — 2.23 million new infections would be expected to occur over an 11-month period without any other mitigation measures in place, like mask wearing or gathering restrictions. But under that same vaccination scenario, with those other mitigation measures in place, only about 800,000 new infections would be expected — 64% fewer. Without these other mitigation measures, over 15,000 deaths from COVID-19 would be expected.
In contrast, under the model’s best-case vaccination scenario of 90% efficacy and 75% of the population vaccinated, about 527,000 new infections would be expected without any other mitigation measures. With extra mitigation measures like mask wearing and physical distancing, that number would drop to about 451,000 — only 15% fewer infections. Under this best-case scenario with extra mitigation measures, about 6,800 deaths from COVID-19 would be expected. As the comparison between the worst-case and best-case scenarios for vaccination shows, with less effective vaccines and fewer people getting them, mitigation measures like mask wearing become more important for stopping the spread of COVID-19 and saving lives. On the other hand, if COVID-19 vaccines prove highly protective going forward and lots of people get them, other mitigation measures will have a much smaller impact on new infections.
“Our findings highlight the importance of continued adherence to [mitigation measures] while the population is vaccinated, particularly under scenarios of lower vaccine efficacy and coverage,” the researchers concluded. “Premature removal of [these measures] could result in a resurgence of infections with a magnitude exceeding that before vaccine distribution.”
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