TABLE 1. Cohort sizes and cohort-specific incident laboratory-confirmed COVID-19 cases in California (N = 752,781) and New York (N = 355,819) and hospitalizations in California (N = 56,177) — May 30–November 20, 2021.
| State/Vaccination and diagnosis status*,† | No. of persons in each cohort (%) | Incident
laboratory-confirmed COVID-19 cases |
Incident COVID-19
hospitalizations** |
||
|---|---|---|---|---|---|
| No. (cumulative incidence)§,¶ | Median (IQR) interval from vaccination to positive test, days | Median (IQR) interval from previous diagnosis to positive test, days | No. (cumulative incidence)§,¶ | ||
|
California
| |||||
|
Vaccinated
| |||||
| Previous COVID-19
diagnosis |
968,167 (4.5) |
3,471 (3.6) |
138 (95–181) |
262 (218–322) |
273 (0.3) |
| No previous diagnosis |
15,484,235 (71.2) |
240,045 (15.5) |
150 (112–189) |
NA |
10,737 (0.7) |
|
Unvaccinated
| |||||
| Previous COVID-19
diagnosis |
1,370,782 (6.3) |
6,805 (5.0) |
NA |
277 (229–356) |
378 (0.3) |
| No previous diagnosis |
3,911,146 (18.0) |
502,460 (128.5) |
NA |
NA |
44,789 (11.5) |
|
New
York
| |||||
|
Vaccinated
| |||||
| Previous COVID-19
diagnosis |
485,649 (4.5) |
2,355 (4.9) |
162 (118–201) |
276 (227–348) |
NA |
| No previous diagnosis |
7,809,968 (72.2) |
142,388 (18.2) |
171 (133–203) |
NA |
NA |
|
Unvaccinated
| |||||
| Previous COVID-19
diagnosis |
527,140 (4.9) |
3,250 (6.2) |
NA |
295 (242–427) |
NA |
| No previous diagnosis | 1,993,709 (18.4) | 207,826 (104.2) | NA | NA | NA |
Abbreviations: NA = not applicable; NAAT = nucleic acid amplification test.
* Statewide immunization databases in California are the California Immunization Registry, Regional Immunization Data Exchange, and San Diego Immunization Registry, and the laboratory system is the California COVID Reporting System; in New York, Immunization Information Systems include Citywide Immunization Registry and the New York State Immunization Information System; the laboratory system is the Electronic Clinical Laboratory Reporting System. California data were matched between the immunization and case registries using a probabilistic algorithm with exact match for zip code and date of birth and fuzzy match on first name and last name. New York data were matched to the Electronic Clinical Laboratory Reporting System with the use of a deterministic algorithm based on first name, last name, and date of birth. In California, person-level hospitalization data from the California COVID Reporting System and supplemental hospitalization reports were used to identify COVID-19-associated hospitalizations.
† For both classification into cohorts of persons with previous COVID-19 diagnoses and for measuring incident cases, laboratory-confirmed infection was defined as the receipt of a new positive SARS-CoV-2 NAAT or antigen test (both for New York and NAAT only for California) result, but not within 90 days of a previous positive result. Fully vaccinated is defined as having received a second dose of an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna) or 1 dose of the Janssen (Johnson & Johnson) vaccine ≥14 days before May 30, 2021. Whereas vaccinated cohorts were directly observed in the immunization information system databases, unvaccinated persons without a previous COVID-19 diagnosis were defined using U.S. Census population estimates minus persons partially or fully vaccinated by December 11, 2021, and unvaccinated persons with a previous laboratory-confirmed infection before May 30, 2021. In California, the California Department of Finance population estimates were used for 2020, and the 2018 CDC National Center for Health Statistics Bridged Race file for census population estimates were used in New York, consistent with other COVID-19 surveillance reporting.
§ Cumulative cases per 1,000 persons.
¶ These summaries of cumulative incidence are estimated across a period of variability in the epidemic for all cohorts.
** Hospitalization data for New York are not included in this analysis.