Estimation of COVID-19 vaccine effectiveness against hospitalisation in individuals aged ≥ 65 years using electronic health registries; a pilot study in four EU/EEA countries, October 2021 to March 2022

Abstract

By employing a common protocol and data from electronic health registries in Denmark, Navarre (Spain), Norway and Portugal, we estimated vaccine effectiveness (VE) against hospitalisation due to COVID-19 in individuals aged ≥ 65 years old, without previous documented infection, between October 2021 and March 2022. VE was higher in 65–79-year-olds compared with ≥ 80-year-olds and in those who received a booster compared with those who were primary vaccinated. VE remained high (ca 80%) between ≥ 12 and < 24 weeks after the first booster administration, and after Omicron became dominant.

Risk reduction of hospitalisation and severe disease in vaccinated COVID-19 cases during the SARS-CoV-2 variant Omicron BA.1-predominant period, Navarre, Spain, January to March 2022

“…Moreover, a booster dose of COVID-19 vaccine was shown to be more relevant to maintain protection against disease caused by the Omicron variant [13][14][15]. Our results are aligned with other studies that have evaluated COVID-19 vaccine effectiveness in preventing COVID-19 hospitalisation and severe outcomes during the Omicron period [23][24][25][26]. The findings of our study were consistent regardless of whether or not selftest results were included.…”

“…The enhanced surveillance covered all COVID-19 cases confirmed in the region, and during the study period, there was high availability of diagnostic tests and of personnel for testing of all suspected cases, and only hospitalisations, ICU admissions and deaths related to COVID-19 according to a medical revision were considered. Our results may be of interest to other countries, since the variant distribution observed was similar to that described in Europe [ 23 - 25 ].…”

Seroprevalence of antibodies against SARS-CoV-2 and risk of COVID-19 in Navarre, Spain, May to July 2022

“…Vaccine-induced immunity has demonstrated high effectiveness in preventing severe COVID-19 outcomes regardless of the SARS-CoV-2 variant [15,16]. The present results show that vaccine-induced immunity has insufficient effect for preventing SARS-CoV-2 infections during the circulation of the Omicron BA.4 and BA.5 subvariants, while immunity induced by natural infection considerably reduces the risk of infection.…”

COVID-19 mRNA vaccine effectiveness (second and first booster dose) against hospitalisation and death during Omicron BA.5 circulation: cohort study based on electronic health records, Portugal, May to July 2022

“…In the group aged 60-79 years, and given that the VE estimates against hospitalisation were lower for the first booster dose compared with early stages of the first booster dose roll-out (74% vs 95%) [11], the recommendation of extending the second booster dose to this age group could have a relevant benefit in terms of COVID-19 impact mitigation.…”

“…For the population aged 80 years and older, our study supports a high VE of the second mRNA booster dose in preventing severe COVID-19-related outcomes, and a relevant increase in protection compared with previous vaccination during Omicron BA.5 predominance. In the group aged 60–79 years, and given that the VE estimates against hospitalisation were lower for the first booster dose compared with early stages of the first booster dose roll-out (74% vs 95%) [ 11 ], the recommendation of extending the second booster dose to this age group could have a relevant benefit in terms of COVID-19 impact mitigation.…”