Vaccine breakthrough cases are defined as instances in which an individual tested positive for COVID-19 after being fully-vaccinated (more than 14 days after completing their vaccine series). This report details the levels of such cases, and hospitalizations among fully-vaccinated people, in New York State. This information has been ascertained by matching records in statewide immunization databases with statewide testing and daily hospital reporting systems.
These findings demonstrate that such cases and hospitalizations have occurred in New York State, but at levels substantially lower than among unvaccinated people. This is because COVID-19 vaccines are working to protect the health of New Yorkers. The estimated high protective effect of vaccines against confirmed infection, and even higher effect for hospitalization, agree with findings from clinical and population studies conducted around the world. Because protection from vaccines is not 100%, additional measures such as mask wearing offer extra protection, particularly in areas of increased transmission.
Updates to this breakthrough data report will be published approximately weekly and include data through the designated “as of” date.
As of data received through October 17, 2021, the New York State Department of Health is aware of:
- 112,966 laboratory-confirmed breakthrough cases of COVID-19 among fully-vaccinated people in New York State, which corresponds to 0.9% of the population of fully-vaccinated people 12-years or older.
- 7,629 hospitalizations with COVID-19 among fully-vaccinated people in New York State, which corresponds to 0.06% of the population of fully-vaccinated people 12-years or older.
These results indicate that laboratory-confirmed SARS-CoV-2 infections and hospitalizations with COVID-19 have been uncommon events among the population of people who are fully-vaccinated (≥14 days after completing their vaccine series).
To understand the above statistics, it is important to consider that they reflect not only the effectiveness of vaccines, but also changes over time in the intensity of the epidemic, circulating variant strains (such as Delta), and protective behaviors (e,g, masking and social distancing) against COVID-19, as well as the growing number of people fully-vaccinated in New York State.
To measure the real-world effectiveness of vaccines in reducing cases and hospitalizations, compared to unvaccinated people, additional information and analyses are necessary.
One approach is to compare the rates of cases and hospitalizations among vaccinated people to the rates of these outcomes in unvaccinated people, over time.
The next section shows these comparisons among adult residents of NYS, building on previously published methods.
Rates of Cases & Hospitalizations
These rates of cases and hospitalizations over time and estimated vaccine effectiveness cover through the week of September 27, 2021 (ending October 3, 2021), to allow enough time for the data needed for valid comparisons to become available in data systems.
Summary of findings for all people age 18 years or older:
- In comparing the rates of laboratory-confirmed COVID-19 cases between fully-vaccinated and unvaccinated people using the vaccine effectiveness measure, fully-vaccinated New Yorkers continue to be strongly protected against infection.
- For the week of May 3, 2021, the estimated vaccine effectiveness shows fully-vaccinated New Yorkers had a 91.8% lower chance of becoming a COVID-19 case, compared to unvaccinated New Yorkers.
- Although this effectiveness measure declined through mid-July, this decline then ceased. In the week of September 27, 2021, fully-vaccinated New Yorkers had a 77.9% lower chance of becoming a COVID-19 case, compared to unvaccinated New Yorkers.
- Comparing the rates of COVID-19 hospitalization between fully-vaccinated and unvaccinated people using age-adjusted vaccine effectiveness, fully-vaccinated New Yorkers remain strongly protected against COVID-19 hospitalization.
- Across the time period of analysis, fully-vaccinated New Yorkers had between an 89.7% and 95.2% lower chance of being hospitalized with COVID-19, compared to unvaccinated New Yorkers.
- Taken together these results demonstrate that vaccines continue to be highly-effective at protecting New York residents from infection and hospitalization with COVID-19. Put simply, these outcomes are occurring among vaccinated people, but at levels far lower than among unvaccinated people, because vaccines work.
- The ongoing >89% effectiveness against hospitalization is consistent with the results of the original vaccine clinical trials’ results, which showed protection from severe COVID-19 disease at these levels.
- Effectiveness against laboratory-confirmed infections is high, but lower than against COVID-19 hospitalization.
- The reasons for changes in this effectiveness estimate are unclear and may be due to declines in immunity from the vaccines, the marked increase in the levels of the Delta variant during this time period (to >99% of specimens in the federal region containing New York State), and/or changes in protective behaviors over time. This is an area of active study by scientists in New York and around the world.
- Role for Additional Protective Measures: Because vaccines do not offer 100% protection, additional protective measures, such as mask wearing, and social distancing will provide additional protection. Please read the CDC's interim public health recommendations for fully vaccinated people.
Table 1: New cases and new hospitalizations with laboratory-confirmed COVID-19 among fully vaccinated and unvaccinated adults, and estimated vaccine effectiveness, age 18 years or older.
Figure 1: New cases with laboratory-confirmed COVID-19 among fully vaccinated and unvaccinated adults, and estimated vaccine effectiveness, age 18 years or older
Figure 2: New hospitalizations with laboratory-confirmed COVID-19 among fully vaccinated and unvaccinated adults, and estimated vaccine effectiveness, age 18 years or older.
Table 2: Estimated vaccine effectiveness for reducing cases and hospitalizations with laboratory-confirmed COVID-19, by age group.
Please refer to our publication in MMWR for a description of the data sources, analytic methods, methodological considerations and limitations of this work.
- All estimates in this report are preliminary and subject to change. In order to confirm vaccination status at the time of diagnosis and/or hospitalization, the dates of these events must be evaluated, as opposed to the dates these cases were reported to NYS DOH. Because of this requirement and ongoing data submissions of infections, hospitalizations, and vaccinations within each respective database, it is expected that historical estimates may need minor changes as this report is updated to provide a timely snapshot of the epidemic.
- The vaccine effectiveness measure, as estimated in this analysis, is a summary comparison among (or of, but not both) those who are fully-vaccinated. This comparison includes all COVID-19 vaccine doses given to New Yorkers and may reflect other behavioral, medical, and exposure differences between fully-vaccinated and unvaccinated people.
- In this analysis, fully-vaccinated is defined as an individual who:
- Has received one of the three vaccines currently authorized by the US Food and Drug Administration (FDA): Pfizer-BioNTech, Moderna, and Janssen/Johnson & Johnson.
- Is 14 days or more past the final dose of their original 2-dose (Pfizer-BioNTech, Moderna) or 1-dose (Janssen/Johnson & Johnson) series.
- Fully-vaccinated people may have received additional doses, which are not currently accounted for in this analysis. We note that additional doses, limited to immunocompromised people, were first authorized by FDA on August 13, 2021 and recommended by ACIP on August 14, 2021, near the end of this analysis timeframe.
- For the purposes of this analysis, cases are defined at the person-level (1 case per person) and hospital admissions are defined at the event-level (multiple admissions with COVID-19 possible per person).