“Control of the COVID-19 pandemic has been impeded by the slow global uptake of targeted vaccines, emergence of more transmissible variants, and resistance to continuation of nonpharmaceutical interventions. Commonly used vaccines can have nonspecific immune effects, and several have been shown to have beneficial heterologous effects against SARS-CoV-2 infection,” wrote authors led by Nathaniel Hupert, MD, MPH, associate professor of population health sciences, Weill Cornell Medicine, in the journal Proceedings of the National Academy of Sciences.“ However, there is no science-based guidance on effective implementation of such heterologous vaccine interventions (HVIs) to counter the current or future pandemics.”
To further investigate the optimal intervention of HVIs in pandemic settings, Hupert and colleagues modeled the effect of different HVI strategies using the COVID-19 International Modeling Consortium (CoMo) system. CoMo is an open-source, age-structured, country-specific, dynamic compartmental model of SARS-CoV-2 transmission and COVID-19 illness, treatment, and mortality.
"If you have a model that can be customized to a particular place and time in the context of an outbreak, you can start to experiment with different conditions of population immunity and see how things might have played out," said Hupert in a Weill Cornell Medicine press release.
Using the fall/winter 2020-2021 COVID-19 wave in the US, researchers modeled the likely effects of an explicitly defined HVI instituted at different times and targeting different populations. Although investigators did not specify particular vaccines, the team chose values for cross-protection that were consistent with data from earlier studies on measles, influenza, tuberculosis, and other recommended vaccinations.
Hupert and colleagues found that HVI campaigns targeted to both elderly and nonelderly (ie, persons aged ≥20 years) populations and starting those campaigns during pandemic growth phases (ie, when the pandemic reproduction number is >1) led to the greatest reduction in COVID-19 morbidity and mortality.
In addition, results showed that HVIs with 5%-15% efficacy could have reduced COVID-19 cases, hospitalizations, and mortality during the 2020-2021 fall/winter wave in the US.
“These results may be generalizable beyond COVID-19 and the US to indicate how even minimally effective heterologous immunization campaigns could reduce the burden of future viral pandemics,” concluded researchers.