Interim analysis of COVID-19 vaccine effectiveness against Severe Acute Respiratory Infection due to laboratory-confirmed SARS-CoV-2 among individuals aged 30 years and older, ECDC multi-country study – second update

Guidance
Cite:

European Centre for Disease Prevention and Control. Interim analysis of COVID-19 vaccine effectiveness against Severe Acute Respiratory Infection due to laboratory-confirmed SARS-CoV-2 among individuals aged 30 years and older, ECDC multi-country study – second update. ECDC: Stockholm; 2022.

This document reports the pooled estimates from the ECDC study of COVID-19 vaccine effectiveness, conducted through the implementation of a multi-country approach using the 'Core protocol for ECDC studies of COVID-19 vaccine effectiveness against hospitalisation with Severe Acute Respiratory Infection laboratory confirmed with SARS-CoV-2, version 1.0'.

This second update contains vaccine effectiveness results among individuals aged 30 years and older, for the pre-Delta and the Delta-dominant periods (3 January–31 May 2021 and 1 July–15 December 2021, respectively). It also contains estimates by COVID-19 vaccine product (i.e. Comirnaty and Vaxzevria). Compared with the previous report, two additional countries submitted data retrospectively (Ireland and the Netherlands); therefore, estimates for the pre-Delta period may differ slightly from those published previously.

Executive summary

Key facts

  • ECDC is building infrastructure to allow regular monitoring of COVID-19 vaccine effectiveness over time, using a multi-country approach that involves studies implemented in different settings [1,2].
  • This update reports on one of the ECDC multi-country studies that is centred around the hospital setting and severe disease, with the aim of assessing vaccine effectiveness against severe acute respiratory infection (SARI) due to laboratory-confirmed SARS-CoV-2. As the study is ongoing, this report contains updated results following those previously published on 8 October 2021 [3] and 20 January 2022 [4].
  • As of 16 January 2022, a total of 11 EU countries are participating in the multicentric study (Belgium, Croatia, Czechia, France, Greece, Ireland, Luxembourg, Malta, the Netherlands, Portugal, Spain).
  • In this third report, results for the 30-49 years age group have been added. As one of the conditions for individuals to be included in the study was their eligibility for COVID-19 vaccination, this age group was previously ineligible for inclusion.
  • The COVID-19 vaccine effectiveness estimates presented are pooled estimates from eight countries (records from three countries were excluded, as fewer than five controls were reported). Compared with the previous report, two additional countries have provided data. This report also covers a longer study period, with vaccine effectiveness estimates for two periods of the pandemic in 2021 (3 January–31 May and 1 July–15 December), as a proxy for the pre-Delta and Delta-dominant periods, respectively.
  • Most individuals enrolled in the study received COVID-19 mRNA vaccine Comirnaty (Pfizer/BioNTech). The effectiveness of full vaccination with the primary series (two doses for vaccines with a two-dose course and one dose for vaccines with a one-dose course) was higher than for partial vaccination (a single dose for those vaccines with a two-dose course) in all age groups included in this analysis (30 years and older), regardless of the study period (pre-Delta and Delta-dominant periods).
  • The results presented in this report suggest a high adjusted vaccine effectiveness in preventing SARI associated with laboratory-confirmed SARS-CoV-2 infection for COVID-19 vaccines deployed during the first 12 months of the vaccination campaign across EU/EEA countries in all age groups 30 years and older, albeit with wide confidence intervals. The adjusted vaccine effectiveness against laboratory-confirmed SARS-CoV-2 among hospitalised SARI patients observed ≥14 days after full vaccination with the primary series of any vaccine product was 93% (95% confidence interval (CI): 86–96%) during the pre-Delta period and 83% (95% CI: 78–87%) during the Delta-dominant period. For Comirnaty, vaccine effectiveness was 94% (95% CI: 88–97%) in the pre-Delta period and 82% (95% CI: 76–87%) in the Delta period. For Vaxzevria, there were no reports of full vaccination with the primary series during the pre-Delta period, but vaccine effectiveness during the Delta period was 79% (95% CI: 69–86%).
  • Results of the analysis by age group, for all vaccine products combined and during the pre-Delta period, showed that adjusted vaccine effectiveness for partial vaccination was higher in those aged 65–79 years than in the other age groups, although all confidence intervals overlap. A similar pattern was observed for full vaccination with the primary series, but very low numbers of fully vaccinated cases in the youngest age group (30–49 years) make these estimates difficult to interpret. For the Delta period, adjusted vaccine effectiveness for full vaccination with the primary series was higher in younger age groups than in older age groups: 55% (95% CI: 25–74) in those aged 80 years and older compared to 91% (95% CI: 81–95) in those aged 30–49 years (for all products combined, although the results for Comirnaty were very similar). The adjusted vaccine effectiveness for Vaxzevria observed ≥14 days after full vaccination with the primary series was 79% (95% CI: 60–89%) in those aged 50–64 years and 87% (95% CI: 73–94%) in those aged 65–79 years. Sample size was insufficient to estimate vaccine effectiveness in other age groups for Vaxzevria during the Delta period.
  • Estimated results were in the range of estimates published in other studies for similar outcomes in this population during the pre-Delta and Delta periods [5–7].