Interim analysis of COVID-19 vaccine effectiveness against Severe Acute Respiratory Infection due to SARS-CoV-2 in individuals aged 20 years and older – third update

Guidance
Cite:

European Centre for Disease Prevention and Control. Interim analysis of COVID-19 vaccine effectiveness against Severe Acute Respiratory Infection due to SARS-CoV-2 in individuals aged 20 years and older – third update. ECDC: Stockholm; 2022.

This update reports on one of the ECDC multi-country studies assessing vaccine effectiveness against severe acute respiratory infection (SARI) due to laboratory-confirmed SARS-CoV-2 in the hospital setting. This is a case-control study using the test-negative design. As the study is ongoing, this report contains updated results following those previously published on 8 October 2021, 20 January 2022 and 14 March 2022.

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 assessing vaccine effectiveness against severe acute respiratory infection (SARI) due to laboratory-confirmed SARS-CoV-2 in the hospital setting. This is a case-control study using the test-negative design. As the study is ongoing, this report contains updated results following those previously published on 8 October 2021 [3], 20 January 2022 [4] and 14 March 2022 [5].
  • As of 7 July 2022 (end data of data submission), a total of 12 EU countries are participating in the multicentre vaccine effectiveness study: Belgium, Croatia, Czechia, France, Germany, Greece, Ireland, Luxembourg, Malta, the Netherlands, Portugal, and Spain.
  • The COVID-19 vaccine effectiveness estimates presented in the report are pooled estimates from eight countries: records from three countries were excluded as fewer than five controls were reported per site, while one country was excluded as the data reported were outside the reporting period. Compared with the previous report, the data presented include a wider age range, including those aged 20-29 years for the first time.
  • This report also covers a shorter study period, focusing on vaccine effectiveness estimates for 21 December 2021– 2 July 2022, as a proxy for the Omicron variant-dominant period (further called the ‘Omicron period’). This report includes effectiveness estimates for primary series vaccination alone, and primary series vaccination with booster doses in patients who were part of their country’s target group for booster dose vaccination at the time of the swab.
  • Most individuals enrolled in the study received COVID-19 mRNA vaccine Comirnaty (Pfizer/BioNTech). The effectiveness of full vaccination with the primary series only (two doses for vaccines with a two- dose course and one dose for vaccines with a one-dose course) was lower than for primary series with booster overall in all age groups included in this analysis (20 years of age and older).
  • The adjusted vaccine effectiveness against laboratory-confirmed SARS-CoV-2 among hospitalised SARI patients during the Omicron period observed ≥150 days after full vaccination with only the primary series of any vaccine product was 45% (95% confidence interval (CI): 27–58%); while it was 65% (95% CI: 56–72%) with the addition of a booster dose. Adjusted vaccine effectiveness was 41% (95% CI: 19–57%) without booster and 60% (95% CI: 50–69%) with a booster dose for Comirnaty; 49% (95% CI: 13–70%) and 75% (95% CI: 06–84%), respectively, for Vaxzevria.
  • Results of the analysis by age group for all vaccine products combined during the Omicron period indicated that adjusted vaccine effectiveness point estimates for complete primary series vaccination without a booster dose was higher in those aged 20–59 years than in other age groups, although all confidence intervals overlap. A similar pattern was observed for full vaccination with primary series plus a booster dose. Estimated results were in the range published in other studies for similar outcomes in this population during the Omicron period.