Thread by @sailorrooscout

A study out of RIVM (Netherlands) shows vaccine efficacy for full vaccination in regards to the Delta variant against ICU admission was 97% and against hospitalization was 95%. Vaccine efficacy was high in ALL age groups and did NOT show waning with time even after four months.🧵

In this study, researchers utilized incidence rates of COVID-19 hospitalizations and ICU admissions by vaccination status and age group to calculate vaccine effectiveness against COVID-19 hospitalizations and ICU admissions by age group, vaccine type (this study includes Moderna

Pfizer, AstraZeneca, and Johnson & Johnson), time since vaccination, and prevailing variant (Alpha or Delta). For the study period 4 April- 29 August 2021, 15,571 hospitalized people with COVID-19 were included in the analysis, of whom 887 (5.7%) were fully vaccinated.

Incidence rates of hospitalizations and ICU admissions per age group and vaccination status were calculated, and vaccine efficacy was determined as 1-incidence rate ratio, and adjusted for calendar date and age group in a negative binomial regression model.

Of 15,571 included patients, 887 (5.7%) were fully vaccinated on the date of disease onset, 1,111 (7.1%) were partly vaccinated and 13,574 (87.2%) were unvaccinated. Of the 13,574 unvaccinated patients, 7,406 were found in the CIMS registry with a vaccination date after

hospitalization. Researchers found vaccine efficacy against hospitalization for full vaccination was 94% (95% CI 93-95%) in the Alpha period and 95% (95% CI 94-95%) in the Delta period. The vaccine efficacy for full vaccination against ICU admission was 93% (95% CI 87-96%)

in the Alpha period and 97% (95% CI 97-98%) in the Delta period. Vaccine efficacy was high in all age groups and did NOT show waning with time since vaccination UP TO (NOT ONLY as this was the length of the study period) 20 weeks (over four months) after full vaccination.

Figure 1a shows that most hospitalized persons were unvaccinated. From July onward, the number of vaccinated patients approaches the number of unvaccinated patients in the age group 70 years and older. However, Figure 1b shows that the incidence rate of hospitalizations per

100.000 person-days is far lower among vaccinated than among unvaccinated persons. The similar numbers in absolute terms in the age group 70 years and older are due to the HIGH vaccination coverage in this group. NOTE: A lot of people tend to miss this point!

With increasing vaccination coverage, the incidence rate in the fully vaccinated population APPROACHES the overall incidence rate in the population (Figure 1b). The more fully vaccinated a population is, the more your population will be classified as just that. The same trends

are visible for ICU admissions (Figure 2a and 2b), although the absolute number of ICU admissions in vaccinated persons was still well below the number of ICU admissions in unvaccinated persons.

Conclusion: This study using nationwide surveillance data found 95% and 97% effectiveness of the COVID-19 vaccines used in the Netherlands against hospitalization and ICU admission, respectively. This high VE persisted into the Delta period and OVER 20 weeks after full

vaccination. Researcher’s findings are in line with previous studies showing that while VE against SARS-CoV-2 infection is lower with Delta compared to Alpha variant, the VE against severe disease remains very high. A study from Israel did indicate possible waning over time of VE

against severe COVID-19 over time. In their data, adjusting for 5-year age groups, researchers here did not observe such waning even UP TO (NOT ONLY mind you) 20-plus weeks after full vaccination. You can find this study here: medrxiv.org/content/10.110…