What is a Post-Vaccination COVID-19 Case?
Post-vaccination cases are defined as individuals who are fully vaccinated and have a positive SARS-CoV-2 molecular (e.g. PCR) test 14 days or more after they have completed their full one-dose or two-dose COVID-19 vaccination series. They are also referred to as vaccine breakthrough cases.
How are Post-Vaccination COVID-19 Cases Identified?
The California Department of Public Health (CDPH) is identifying post-vaccination cases by analyzing the immunization and case registries to find individuals who have a positive SARS-Cov-2 molecular test at least 14 days after they have completed their full vaccination series. Local Health Jurisdictions (LHJs) are also encouraged to alert CDPH of post-vaccination cases especially if they result in severe disease (e.g., hospitalization or death) or if they are associated with an outbreak.
Why are we Tracking Post-Vaccination Cases?
Tracking cases of COVID-19 that occur after vaccination is important for monitoring the immunization campaign. While COVID-19 vaccines are safe and effective, some cases are still expected in persons who have been vaccinated, as no vaccine is 100% effective. If the number or severity of post-vaccination cases exceeds expected levels, this could be a signal of reduced protection against a variant or errors in vaccine delivery. Whole genome sequencing of post-vaccination cases, especially severe cases, can help characterize the effectiveness of current vaccines against variants.
What is the Current Data on Post-Vaccination Cases in California?
For the week of August 29-September 4, 2021, the average daily COVID-19 case rate among unvaccinated Californians age 16 or older is 71.03 per 100,000 and the average daily COVID-19 case rate among fully vaccinated Californians age 16 or older is much lower at 8.9 per 100,000.
Between January 01, 2021 and September 12, 2021 in California,
- Out of over 23.1 million fully vaccinated individuals, 144,957 post-vaccination cases (0.6%) have been identified.
- At least 3,751 individuals identified as post-vaccination COVID-19 cases were hospitalized. However, it is important to note that approximately 65% of cases have missing hospitalization data. It is also important to note that a post-vaccine case may have been hospitalized for a condition unrelated to COVID-19 reason but were tested for COVID-19 upon admission.
- Among post-vaccination cases identified, at least 500 people have died. However, it is unknown if the primary cause of death in these cases was COVID-19 or if there were other contributory or alternate causes.