[ad_1]
An estimated 14.3% of the U.S. population had antibodies to COVID-19 as of mid-November 2020, suggesting the virus has infected many more people than has been reported – but not enough yet. to get closer to the proportion needed for collective immunity, according to a study published today in JAMA network open.
In the cross-sectional study, researchers from study sponsors Pfizer and Merck analyzed data from randomized community seroprevalence surveys and five such regional and national surveys of the Centers for Disease Control and Prevention (CDC) for estimate multipliers of underreporting of infections. Seroprevalence surveys reveal the proportion of a population that has antibodies against a certain disease, such as COVID-19.
After adjusting for underreporting using validated multipliers, the analysis revealed an estimated median of 46,910,006 infections with SARS-CoV-2, the virus that causes COVID-19; 28,122,752 symptomatic infections; 956,174 hospitalizations; and 304,915 deaths from April to mid-November.
According to these figures, 14.3% of Americans had been infected with the novel coronavirus as of November 15, 8.6% had symptomatic infections, with an infection-to-hospitalization ratio of 2.0% and a case fatality rate for those with symptoms of 1.1%.
In contrast, the CDC reported 10,846,373 cases of COVID-19 and 244,810 deaths during the same period, with 1,037,962 cases recorded in the last 7 days of that period (on average, 148,280 new cases reported daily).
An estimated 35% of unreported COVID deaths
The authors noted that seroprevalence surveys are essential for tracking progress towards herd immunity, which occurs when about 60% of a population has antibodies that can help slow community transmission. In comparison, the number of reported cases is underestimated due to the fact that many symptomatic people do not seek screening or medical attention, and the estimated 40% do not have any symptoms.
“The American population stays away from herd immunity, even with millions of new infections every week,” the researchers wrote. “The estimated number of COVID-19 deaths is also remarkably higher than the reported deaths in the United States through November 15, 2020, confirming the conclusion that approximately 35% of COVID-19 deaths go unreported.
They added that several methodological issues must be considered when using seroprevalence surveys to derive underreporting multipliers to adjust disease surveillance data to estimate disease burden. These problems include the time between infection and antibody development, the decrease in antibodies, and the reporting of confirmed infections. Multipliers also change over time with changes in the proportion of the population that has been tested, diagnosed, and reported.
“A sensitivity analysis of CDC seroprevalence surveys suggested that using the number of cases reported at the end of the survey period provides a useful estimate of underreporting multipliers, particularly at the onset of the pandemic.” , said the authors. “Therefore, the number of cases reported on the last day of the seroprevalence survey was used in estimating the COVID-19 disease burden in this study.”
The researchers concluded that surveillance should continue to measure progress towards herd immunity. “Additional seroprevalence surveys are needed to monitor the pandemic, including after the development of safe and effective vaccines,” they said.
[ad_2]
Source link