Age and product dependent vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adults in Norway: a national cohort study, July–November 2021

Abstract

Background COVID-19 vaccines have been crucial in the pandemic response and understanding changes in vaccines effectiveness is essential to guide vaccine policies. Although the Delta variant is no longer dominant, understanding vaccine effectiveness properties will provide essential knowledge to comprehend the development of the pandemic and estimate potential changes over time. Methods In this population-based cohort study, we estimated the vaccine effectiveness of Comirnaty (Pfizer/BioNTech; BNT162b2), Spikevax (Moderna; mRNA-1273), Vaxzevria (AstraZeneca; ChAdOx nCoV-19; AZD1222), or a combination against SARS-CoV-2 infections, hospitalisations, intensive care admissions, and death using Cox proportional hazard models, across different vaccine product regimens and age groups, between 15 July and 31 November 2021 (Delta variant period). Vaccine status is included as a time-varying covariate and all models were adjusted for age, sex, comorbidities, county of residence, country of birth, and living conditions. Data from the entire adult Norwegian population were collated from the National Preparedness Register for COVID-19 (Beredt C19). Results The overall adjusted vaccine effectiveness against infection decreased from 81.3% (confidence interval (CI): 80.7 to 81.9) in the first 2 to 9 weeks after receiving a second dose to 8.6% (CI: 4.0 to 13.1) after more than 33 weeks, compared to 98.6% (CI: 97.5 to 99.2) and 66.6% (CI: 57.9 to 73.6) against hospitalisation respectively. After the third dose (booster), the effectiveness was 75.9% (CI: 73.4 to 78.1) against infection and 95.0% (CI: 92.6 to 96.6) against hospitalisation. Spikevax or a combination of mRNA products provided the highest protection, but the vaccine effectiveness decreased with time since vaccination for all vaccine regimens. Conclusions Even though the vaccine effectiveness against infection waned over time, all vaccine regimens remained effective against hospitalisation after the second vaccine dose. For all vaccine regimens, a booster facilitated recovery of effectiveness. The results from this support the use of heterologous schedules, increasing flexibility in vaccination policy.

Waning of vaccine effectiveness against moderate and severe covid-19 among adults in the US from the VISION network: test negative, case-control study

“… 10 11 12 13 Our results are also consistent with other reports of waning protection after three mRNA doses. 23 24 25 As with others, we noted less waning against more severe outcomes, 3 26 lower vaccine effectiveness among individuals who were immunocompromised, 17 27 and higher vaccine effectiveness among recipients of mRNA-1273 compared with recipients of BNT162b2. 10 23 24 We also observed improvement in vaccine effectiveness after a fourth dose.…”

Timing of last COVID-19 vaccine dose and SARS-CoV-2 breakthrough infections in fully (boosted) vaccinated healthcare personnel

“…Lastly, we did not restrict our analysis to the 95% of HCP who have been vaccinated with the BNT 162b2 mRNA vaccine only. However, large population studies support the use of heterologous vaccine schedules [ 23 , 24 ].…”

Comparative effectiveness of heterologous booster schedules with AZD1222, BNT162b2, or mRNA-1273 vaccines against COVID-19 during omicron predominance in the Nordic countries

“…Data to assess the effectiveness of heterologous booster schedules, however, are sparse and mainly limited to studies conducted during periods of delta variant predominance and/or as compared with unvaccinated. [10][11][12][13][14][15]17,18] To our knowledge, no study has reported the effectiveness of the individual heterologous booster schedules with the AZD, BNT, and MOD vaccines as compared with primary schedules during an omicron period. When compared with unvaccinated, heterologous and homologous schedules showed similar levels of improved protection against omicron infection[17] and severe COVID-19 [18].…”

“…[6][7][8][9] How these immunologic findings translate into effectiveness is less certain. [10][11][12][13][14][15][16] The use of heterologous booster strategies facilitates a more flexible approach for vaccination roll-out and simplifies logistics, but should be supported by evidence of effectiveness including protection against the omicron variant of concern. This evidence is currently lacking.…”