Question: Do we know what percentage of people with full vaccination and a booster are getting the virus vs. those who are completely unvaccinated vs. those who are fully vaccinated but not yet boosted?

Answer: We don’t have great national-level data and reporting on breakthrough infections and hospitalizations by vaccination status.  CDC presents updated charts on this very topic monthly(ish), but hasn’t presented an update since mid-November (i.e., pre-Omicron dominance).  Those data indicated that compared with fully vaccinated people, unvaccinated individuals had 5x the risk of becoming infected and 14x the risk of dying.  As of end-October (when booster doses were recommended for a subset of adults), CDC estimates that COVID-related deaths per 100,000 pop. were 6.03 among unvaccinated, 0.53 among fully vaccinated, and 0.14 among fully vaccinated plus booster dose (Figure 1); booster doses reduce risk of severe outcomes.  Despite limited national-level data, we do have relatively comprehensive data at the state-level and we also have several relevant scientific studies.  Here is a synthesis of data from two states– New York and Virginia– and a study from the UK, all of which indicate that though breakthrough cases are increasing, vaccine effectiveness against hospitalization remains robust. 

• The New York State Department of Health presents cases and hospitalizations by vaccination status, though it doesn’t capture booster status (Figure 2).  As you can see from the two line graphs, vaccine effectiveness against infection has decreased in the face of omicron.  Meanwhile, vaccine effectiveness against hospitalization is still very high.  With omicron, fully vaccinated New Yorkers have about a 78% lower chance of being hospitalized for COVID as compared with unvaccinated New Yorkers. 
  •  The NY DOH reports “As of data received through January 17, 2022, the New York State Department of Health is aware of:
    • 1,023,704 laboratory-confirmed breakthrough cases of COVID-19 among fully-vaccinated people in New York State, which corresponds to 7.7% of the population of fully-vaccinated people 12-years or older.
    • 30,005 hospitalizations with COVID-19 among fully-vaccinated people in New York State, which corresponds to 0.23% of the population of fully-vaccinated people 12-years or older.
• The Virginia DOH presents similar trends among Virginians, stating “As of 1/08/2022, 5,795,428 Virginians have been fully vaccinated against COVID-19. Of these people, 1.9% have developed COVID-19, 0.053% have been hospitalized, and 0.0172% have died.”  For the week ending on 1/8/2022, unvaccinated people had 35x the risk of hospitalization compared with vaccinated people. 
• The UK studied the risk of hospitalization due to omicron by booster status, finding that ” After 3 doses of vaccine, the risk of hospitalisation for a symptomatic case identified with Omicron through community testing was estimated to be reduced by 68% (42 to 82%) when compared to similar individuals with Omicron who were not vaccinated (after adjusting for age, gender, previous positive test, region, ethnicity, clinically extremely vulnerable status, risk group status and period). Combined with the protection against becoming a symptomatic case, this gives a vaccine effectiveness against hospitalisation of 88% (78 to 93%) for Omicron after 3 doses of vaccine.” 

Figure 1. Rates of Death by Vaccination Status, Booster Status, September 19 – October 30, 2021 (from CDC)

Figure 2. Trends in Cases and Hospitalizations by Vaccination Status, New York State (from NY DOH)