Published on in Vaccine Update for Healthcare Providers
To determine the percentage of the population that has been either naturally infected with SARS-CoV-2 virus or immunized with SARS-CoV-2 vaccines, researchers from the Centers for Disease Control and Prevention (CDC) evaluated blood donations from all 50 states (Jones JM, Stone M, Sulaeman H, et al. Estimated US infection- and vaccine-induced SARS-CoV-2 seroprevalence based on blood donations, July 2020-May 2021. JAMA. 2021 Oct 12;326(14):1400-1409). About 1.5 million blood specimens were examined. Sera containing antibodies against the SARS-CoV-2 nucleoprotein were considered to have come from people who had been naturally infected, whereas sera containing antibodies to the SARS-CoV-2 spike protein but not the nucleoprotein were considered to have come from people who had been vaccinated but not naturally infected.
The authors found that the overall infection-induced SARS-CoV-2 seroprevalence rose from 3.5% in July 2020 to 20.1% in May 2021. The combined infection- and vaccination-induced seroprevalence estimate in May 2021 was 83.3%. Both infection and immunization likely induce protective immunity. These findings show that 83% population immunity is not enough to significantly slow this pandemic.
Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.
You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.