At least twice as many people in the U.S. may have developed antibodies against the novel coronavirus than official numbers suggest, according to a new study.
Researchers looked at results of tests that determine if someone has been infected and if their body has produced immune cells that can protect them from being reinfected.
Results, which were analyzed through September 30 of last year, showed that 6.6 percent of people have antibodies against the virus.
That’s more than double the 2.1 percent of Americans with confirmed cases of COVID-19 at the time.
The team, from Clinical Reference Laboratory Inc, based in Lenexa, Kansas, says this means the true number of infections in the country could be closer to 60 million.
However, this would mean that only 18 percent of the population has been infected, which is still a long way from herd immunity.
A new study looked at 61,910 participants who were tested for antibodies to coronavirus through September 30, 2020, and 6.6%, tested positive. Pictured: A healthcare worker draws blood from a Los Angeles County Sheriff during antibody testing in Pico Rivera, California, February 2021
New York had the highest rate of positive antibody tests at 14.4% and Alaska had the lowest rate at 0% (above). Researchers say their findings suggest 15.9 million people were infected with COVID-19 through September 30 rather than the 7.1 million confirmed cases
Antibody tests, which are known as a serology test, looks for antibodies against the novel coronavirus.
Blood is collected through a vein, and can only be analyzed in a certified laboratory. It looks to see if someone has ever been exposed and is now immune.
Some tests identify the IgG antibody, a protein that the body produces in the late stages of infection and may remain for up to months and possibly years after a person has recovered.
Others detect the the antibody, IgM, which is made by the body a few days after infection.
Health officials say the test could help scientists understand how widespread the virus is, how many people come into contact with the virus and don’t get sick, and how long patients remain immune after they recover.
For the study, published in JAMA Network Open, the team looked at 61,910 participants who were tested for antibodies to the virus, known as SARS-CoV-2 through September 30, 2020.
The test used, from Roche Diagnostics, were had a reported sensitivity rate and specificity rate of 99.5 percent and 99.8 percent, respectfully.
Sensitivity is how often the test correctly determines people who’ve been infected in the past and specificity is how the test identifies those who’ve never been infected.
Of the patients, 4,094 tested positive for antibodies.
Among demographic groups, slightly more women than men were found to have antibodies at 6.9 percent compared to 6.4 percent.
In addition, those older than age 70 had the lowest rate at 2.8 percent and those younger than age 30 years had the highest rate at 9.8 percent.
Researchers also looked at the number of people who tested positive for antibodies based on state.
New York had the highest rate at 14.4 percent, which is unsurprising considering that the state had the highest cumulative number of infections at the time.
Rounding out the top five were Louisiana, Nevada, Florida and Mississippi.
Alaska had the lowest rate at zero percent, but only 85 people were tested for antibodies. The other four states with the lowest rates were Maine Oregon, Hawaii and New Mexico.
Based on the findings, the team believes there were 15.9 million asymptomatic or undiagnosed COVID-19 infections in the U.S. as of September 30, 2020.
That’s more than double the 7.1 million confirmed infections at the time, based on Johns Hopkins University data.
It also means that the true number of cases in the U.S. could actually be closer to 60 million rather than the 29.4 million that are confirmed.
‘Our estimate implied more than twice the number of infections than cases reported to Centers for Disease Control and Prevention, suggesting a more widespread pandemic,’ the authors wrote.
‘The findings of this cross-sectional study suggest that, based on a sample from an otherwise healthy population, the overall number of SARS-CoV-2 infections in the US may be substantially higher than estimates based on public health case reporting.’