At least 58% of U.S. population has natural antibodies from previous Covid infection, CDC says
Seroprevalence of Infection-Induced SARS-CoV-2 Antibodies...
"During September–December 2021, overall seroprevalence increased by 0.9–1.9 percentage points per 4-week period. During December 2021–February 2022, overall U.S. seroprevalence increased from 33.5% (95% CI = 33.1–34.0) to 57.7% (95% CI = 57.1–58.3). Over the same period, seroprevalence increased from 44.2% (95% CI = 42.8–45.8) to 75.2% (95% CI = 73.6–76.8) among children aged 0–11 years and from 45.6% (95% CI = 44.4–46.9) to 74.2% (95% CI = 72.8–75.5) among persons aged 12–17 years (Figure). Seroprevalence increased from 36.5% (95% CI = 35.7–37.4) to 63.7% (95% CI = 62.5–64.8) among adults aged 18–49 years, 28.8% (95% CI = 27.9–29.8) to 49.8% (95% CI = 48.5–51.3) among those aged 50–64 years, and from 19.1% (95% CI = 18.4–19.8) to 33.2% (95% CI = 32.2–34.3) among those aged ≥65 years.
The findings in this report are subject to at least four limitations. First, convenience sampling might limit generalizability. Second, lack of race and ethnicity data precluded weighting for these variables. Third, all samples were obtained for clinical testing and might overrepresent persons with greater health care access or who more frequently seek care. Finally, these findings might underestimate the cumulative number of SARS-CoV-2 infections because infections after vaccination might result in lower anti-N titers,§§,¶¶ and anti-N seroprevalence cannot account for reinfections.
As of February 2022, approximately 75% of children and adolescents had serologic evidence of previous infection with SARS-CoV-2, with approximately one third becoming newly seropositive since December 2021. The greatest increases in seroprevalence during September 2021–February 2022, occurred in the age groups with the lowest vaccination coverage; the proportion of the U.S. population fully vaccinated by April 2022 increased with age (5–11, 28%; 12–17, 59%; 18–49, 69%; 50–64, 80%; and ≥65 years, 90%).*** Lower seroprevalence among adults aged ≥65 years, who are at greater risk for severe illness from COVID-19, might also be related to the increased use of additional precautions with increasing age (3).
These findings illustrate a high infection rate for the Omicron variant, especially among children. Seropositivity for anti-N antibodies should not be interpreted as protection from future infection.
- Three out of every 5 people in the U.S. now have antibodies from a previous Covid-19 infection, according to a new CDC analysis.
- The proportion is even higher among children, demonstrating how widespread the virus was during the winter omicron surge.
- CDC officials told reporters on a call Tuesday that the study did not measure whether people with prior infections had high enough antibody levels to protect against reinfection and severe illness.
- However, CDC Director Dr. Rochelle Walensky said health officials believe there is a lot of protection against the virus in communities from vaccination, boosting and infection taken together.
Seroprevalence of Infection-Induced SARS-CoV-2 Antibodies...
"During September–December 2021, overall seroprevalence increased by 0.9–1.9 percentage points per 4-week period. During December 2021–February 2022, overall U.S. seroprevalence increased from 33.5% (95% CI = 33.1–34.0) to 57.7% (95% CI = 57.1–58.3). Over the same period, seroprevalence increased from 44.2% (95% CI = 42.8–45.8) to 75.2% (95% CI = 73.6–76.8) among children aged 0–11 years and from 45.6% (95% CI = 44.4–46.9) to 74.2% (95% CI = 72.8–75.5) among persons aged 12–17 years (Figure). Seroprevalence increased from 36.5% (95% CI = 35.7–37.4) to 63.7% (95% CI = 62.5–64.8) among adults aged 18–49 years, 28.8% (95% CI = 27.9–29.8) to 49.8% (95% CI = 48.5–51.3) among those aged 50–64 years, and from 19.1% (95% CI = 18.4–19.8) to 33.2% (95% CI = 32.2–34.3) among those aged ≥65 years.
The findings in this report are subject to at least four limitations. First, convenience sampling might limit generalizability. Second, lack of race and ethnicity data precluded weighting for these variables. Third, all samples were obtained for clinical testing and might overrepresent persons with greater health care access or who more frequently seek care. Finally, these findings might underestimate the cumulative number of SARS-CoV-2 infections because infections after vaccination might result in lower anti-N titers,§§,¶¶ and anti-N seroprevalence cannot account for reinfections.
As of February 2022, approximately 75% of children and adolescents had serologic evidence of previous infection with SARS-CoV-2, with approximately one third becoming newly seropositive since December 2021. The greatest increases in seroprevalence during September 2021–February 2022, occurred in the age groups with the lowest vaccination coverage; the proportion of the U.S. population fully vaccinated by April 2022 increased with age (5–11, 28%; 12–17, 59%; 18–49, 69%; 50–64, 80%; and ≥65 years, 90%).*** Lower seroprevalence among adults aged ≥65 years, who are at greater risk for severe illness from COVID-19, might also be related to the increased use of additional precautions with increasing age (3).
These findings illustrate a high infection rate for the Omicron variant, especially among children. Seropositivity for anti-N antibodies should not be interpreted as protection from future infection.
