Since the SARS-CoV-2 epidemic began, there has been an extreme strain on hospitals and medical professionals and many lives have been impacted. Two main intervention methods have been implemented to reduce the spread and severity of SARS-CoV-2: vaccination and non-pharmaceutical interventions, such as social distancing, quarantining, and hygienic measures.Periodic surges in SARS-CoV-2 cases can be anticipated in future years, but the spikes can be reduced by utilizing these public health interventions.
CEID’s Andreas Handel worked with a team of modeling and public health experts from across the United States to analyze how non-pharmaceutical interventions (NPIs) and utilization of vaccine booster doses may impact future transmission waves as new variants emerge.
This model included seven different compartments an individual may be categorized as. At first, many individuals are susceptible to a SARS-CoV-2 infection, categorizing them in the susceptible [S] compartment. Once exposed, individuals have a latent period [E] where they are unable to spread the virus to others. These exposed individuals will either develop an asymptomatic infection [A] or a symptomatic infection [I]. The model assumes that everyone in the asymptomatic compartment will recover and enter the [R] class. Symptomatic individuals will also either recover [R] or need to be hospitalized [H]. Those that are hospitalized [H] will either recover [R] or die [D]. These recovered individuals [R] will become more susceptible to infection [S] once their immunity begins decreasing, depending on their vaccine status. The three levels of these classes for susceptible individuals were unvaccinated, vaccinated, or vaccinated and boosted.
The model closely reflects the true number of peak daily hospitalizations and deaths observed from the Omicron variant wave in January and February of 2022. The peak number of daily deaths at the time was around 2200 people. This model also predicted an increase in cases in June of 2022, due to relaxed NPIs and decreases in natural immunity. Daily deaths were predicted to increase from 520 to 1064 per day. The model found that booster doses significantly impact the intensity of these waves, with an 18% lower rate of daily deaths when boosters were used. A new wave was also expected in autumn of 2022, as seasonal changes in transmission occur. Results from this modeling showed that cumulative deaths could be reduced by 30% with a high uptake of booster doses and non-pharmaceutical interventions.
In addition, utilization of NPIs also reduced the overall number of SARS-CoV-2 infections. NPIs were predicted to reduce infections between July 2022 and January 2023 between 11-16%. These non-pharmaceutical interventions are most beneficial during high transmission periods. Although vaccines are not as effective at reducing infection, research indicates that they still protect against severe illness among variants.
The simulations produced by this research team suggest that there are likely to be SARS-CoV-2 resurgences in the summer, as NPIs are relaxed, and in the autumn, when seasonal circumstances increase transmission rates. Use of NPIs and vaccines continue to be effective to reduce the burden on public health as future SARS-CoV-2 surges occur.
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By: Brenna Daly