ABSTRACT
BackgroundBy March 2023, 54 countries, areas and territories (thereafter "CAT") reported over 2.2 million coronavirus disease 2019 (COVID-19) deaths to the World Health Organization (WHO) Regional Office for Europe (1). Here, we estimate how many lives were directly saved by vaccinating adults in the Region, from December 2020 through March 2023. MethodsWe estimated the number of lives directly saved by age-group, vaccine dose and circulating Variant of Concern (VOC) period, both regionally and nationally, using weekly data on COVID-19 mortality and COVID-19 vaccine uptake reported by 34 CAT, and vaccine effectiveness (VE) data from the literature. We calculated the percentage reduction in the number of expected and reported deaths. FindingsWe found that vaccines reduced deaths by 57% overall (CAT range: 15% to 75%), representing [~]1.4 million lives saved in those aged [≥]25 years (range: 0.7 million to 2.6 million): 96% of lives saved were aged [≥]60 years and 52% were aged [≥]80 years; first boosters saved 51%, and 67% were saved during the Omicron period. InterpretationOver nearly 2.5 years, most lives saved by COVID-19 vaccinationwere in older adults by first booster dose and during the Omicron period, reinforcing the importance of up-to-date vaccination among these most at-risk individuals. Further modelling work should evaluate indirect effects of vaccination and public health and social measures. FundingThis work was supported by a US Centers for Disease Control cooperative agreement (Grant number 6 NU511P000936-02-020), who had no role in data analysis or interpretation. DisclaimerThe authors affiliated with the World Health Organization (WHO) are alone responsible for the views expressed in this publication and they do not necessarily represent the decisions or policies of the WHO. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSSince first identified in late 2019, COVID-19 has caused disproportionately high mortality rates in older adults. With the rapid development and licensing of novel COVID-19 vaccines, immunization campaigns across the WHO European Region started in late 2020 and early 2021, initially targeting the most vulnerable and exposed populations, including older adults, people with comorbidities and healthcare professionals. Several studies have estimated the number of lives saved by COVID-19 vaccination, both at national and multi-country level in the earlier stages of the pandemic. However, only one multi-country study has assessed the number of lives saved beyond the first year of the pandemic, particularly when the Omicron variant of concern (VOC) circulated, a period when vaccination coverage was high in many countries, areas and territories (CAT), but COVID-19 transmission was at its highest. Added value of this studyHere we quantified the impact of COVID-19 vaccination in adults by age-group, vaccine dose and period of circulation of VOC, across diverse settings, using real world data reported by 34 CAT in the WHO European Region for the period December 2020 to April 2023. We estimated that COVID-19 vaccination programs were associated with a 57% reduction (CAT range: 15% to 75%) in the number of deaths among the [≥]25 years old, representing over 1.5 million lives saved (range: 0.7 million to 2.6 million) in 34 European CAT during the first 2.5 years following vaccine introduction. The first booster savedthe most lives (721,122 / 1,408,967, (57%) of all lives saved). The [≥]60 years old age group accounted for 96% of the total lives saved (1,349,617 / 1,408,967) whereas the [≥]80 years old age group represented 52% of the total lives saved (728,858 / 1,408,967 lives saved) and 67% of all lives were saved during the Omicron period (942,571 / 1,408,967). Implications of all the available evidenceOur results reinforce the importance of up-to-date COVID-19 vaccination, particularly among older age-groups. Communication campaigns supporting COVID-19 vaccination should stress the value of COVID-19 vaccination in saving lives to ensure vulnerable groups are up-to-date with vaccination ahead of periods of potential increased transmission.
Subject(s)
COVID-19ABSTRACT
Background: Data on the comparative vaccine effectiveness (CVE) of the bivalent mRNA-booster vaccines containing the original SARS-CoV-2 and omicron BA.4-5 and BA.1 subvariants are limited. Methods: In a period of BA.4-5 subvariants predominance, we estimated the CVE of the bivalent Comirnaty (Pfizer-BioNTech) and Spikevax (Moderna) BA.4-5 and BA.1 mRNA-booster vaccines given as a fourth dose in Denmark, Finland, Norway, and Sweden. From 1 July 2022 to 12 December 2022, we conducted nationwide cohort analyses using target trial emulation to compare risks of Covid-19 hospitalization and death in four-dose (second booster) with three-dose (first booster) vaccinated and between four-dose vaccinated individuals. Results: Compared with having received three vaccine doses, receipt of a bivalent BA.4-5 booster as a fourth dose was associated with a country-combined CVE against Covid-19 hospitalization of 80.5% (95% confidence interval, 69.5% to 91.5%). The corresponding CVE for bivalent BA.1 boosters was 74.0% (68.6% to 79.4%). CVE against Covid-19 death was 77.8% (48.3% to 100%) and 80.1% (72.0% to 88.2%) for bivalent BA.4-5 and BA.1 boosters as a fourth dose, respectively. The CVE of bivalent BA.4-5 vs. BA.1 boosters were 32.3% (10.6% to 53.9%) for Covid-19 hospitalization and 12.3% (-36.1% to 60.7%) for death (the latter estimable in Denmark only). Conclusions: Vaccination with bivalent BA.4-5 or BA.1 mRNA-booster vaccines as a fourth dose was associated with increased protection against Covid-19 hospitalization and death during a period of BA.4-5 predominance. Bivalent BA.4-5 boosters conferred moderately greater vaccine effectiveness against Covid-19 hospitalization compared with bivalent BA.1 boosters.
Subject(s)
Death , COVID-19ABSTRACT
Objective: To investigate the effectiveness of heterologous booster schedules with AZD1222 (Oxford-AstraZeneca, referred to as AZD), BNT162b2 (Pfizer-BioNTech, BNT), and mRNA-1273 (Moderna, MOD) vaccines compared with primary schedules and with homologous mRNA-vaccine booster schedules during a period of omicron predominance. Design: Population-based cohort analyses. Setting: Denmark, Finland, Norway, and Sweden, 27 December 2020 to 28 February 2022. Participants: Adults that had received at least a primary vaccination schedule (ie, two doses) of the AZD, BNT, and/or MOD vaccines during the study period. Main outcome measures: Using the Kaplan-Meier estimator, we compared country-specific risks of SARS-CoV-2 infection and severe COVID-19 outcomes in heterologous booster vaccinated with primary schedule vaccinated (matched analyses) and homologous booster vaccinated (weighted analyses) since emergence of omicron. Results: Heterologous booster schedules improved protection against all outcomes compared with primary schedules, with the largest and most robust effects observed for severe COVID-19. Risk differences for documented infection ranged from -22.4% to -3.1% (comparative vaccine effectiveness [CVE] 9.7% to 60.9%; >63.2% for COVID-19 hospitalisation) across countries for AZD1BNT2BNT3 (AZD as primary dose followed by two doses of BNT) vs AZD1BNT2 and -22.2% to -3.2% (CVE 37.4% to 67.8%; >34.6% for hospitalisation) for BNT1BNT2MOD3 vs BNT1BNT2, the two most common heterologous booster schedules. Heterologous- and homologous booster schedules had comparable effectiveness. Risk differences of documented infection ranged from -0.4% to 4.4% (CVE -20.0% to 2.4%) for AZD1BNT2BNT3 vs BNT1BNT2BNT3 and -19.8% to 1.7% (CVE -14.6% to 53.8%) for BNT1BNT2MOD3 vs BNT1BNT2BNT3; for most comparisons, risk differences for severe COVID-19 outcomes were smaller than 1 per 1000 vaccinated. Previous infection followed by a booster dose conferred the greatest protection. Conclusion: Heterologous booster vaccine schedules are associated with an increased protection against omicron-related COVID-19 outcomes that is comparable to that afforded by homologous booster schedules.
Subject(s)
COVID-19ABSTRACT
Background: COVID-19 vaccines have been crucial in the pandemic response and understanding changes in vaccines effectiveness is essential to guide vaccine policies. Though the Delta variant is no longer dominant, understanding vaccines 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 vaccine effectiveness 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 two to nine 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 wanes 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.
Subject(s)
COVID-19 , Severe Acute Respiratory SyndromeABSTRACT
Background: COVID-19 vaccination was recommended for adolescents in Norway since August 2021. In this population-based cohort study, we estimated the BNT162b2 vaccine effectiveness against any PCR-confirmed (symptomatic or not) SARS-CoV-2 infections caused by the Delta and Omicron variant among adolescents (12-17-years-old) in Norway from August 2021 to January 2022. Methods: Using Cox proportional hazard models, we estimated the BNT162b2 vaccine effectiveness against any Delta and Omicron infections. Vaccine status was included as a time-varying covariate and models were adjusted for age, sex, comorbidities, county of residence, country of birth, and living conditions. Data were obtained from the National Preparedness registry for COVID-19, which contains individual-level data from national health and administrative registries. Findings: Vaccine effectiveness against Delta infection peaked at 68% (95%CI: 64-71%) and 62% (95%CI: 57-66%) in days 21-48 after the first dose among 12-15-year-olds and 16-17-year-olds respectively. Among 16-17-year-olds that received two doses, vaccine effectiveness peaked at 93% (95%CI: 90-95%) in days 35-62 and declined to 84% (95%CI: 76-89%) in 63 days or more after the second dose. For both age-groups, we found no protection against Omicron infection after receiving one dose. Among 16-17-year-olds, vaccine effectiveness against Omicron infection peaked at 53% (95%CI: 43-62%) in 7-34 days after the second dose and decreased to 23% (95%CI: 3-40%) in 63 days or more after vaccination. Vaccine effectiveness decreased with time since vaccination for both variants, but waning was observed to occur faster for Omicron. Interpretation: Our results suggest reduced protection from BNT162b2 vaccination against any SARS-CoV-2 infection caused by the Omicron variant compared to the Delta. In addition, waning immunity was observed to occur faster for Omicron. The impact of vaccination among adolescents on reducing infection and thus transmission is limited during omicron dominance. Funding: No funding was received.
Subject(s)
COVID-19 , Severe Acute Respiratory SyndromeABSTRACT
Understanding the rapid epidemic growth of the novel SARS-CoV-2 Omicron variant is critical for public health management. We compared the secondary attack rate (SAR) of the Omicron and Delta variants in households using Norwegian contact tracing data from December 2021 to January 2022. Omicron SAR was higher (51%) than Delta (36%), with a relative risk (RR) of 1.41 (95% CI 1.27–1.56). We observed increased susceptibility to Omicron infection in household contacts compared to Delta independent of vaccination status; however, considering booster vaccinated contacts, the mean SAR was lower for both variants. We found increased Omicron transmissibility in all vaccination groups of primary cases, except partially vaccinated, compared to Delta. In particular, Omicron SAR for boosted primary cases was high, 46% vs 11% for Delta (RR 4.34; 95% CI 1.52–25.16). In conclusion, booster doses decrease the infection risk of Delta and Omicron but have limited effect in preventing Omicron transmission.
ABSTRACT
We compared the secondary attack rate (SAR) of the SARS-CoV-2 Omicron and Delta variants in households using contact tracing data. Omicron SAR was higher (41%) than Delta (35%), likely due to immune evasion. Booster dose reduces risk of infection but has limited effect on preventing Omicron transmission.
ABSTRACT
Background: SARS-CoV-2 vaccines show high effectiveness against infection and (severe) disease. However, few studies estimate population level vaccine effectiveness against multiple COVID-19 outcomes, by age and including homologous and heterologous vaccine regimens. Methods: Using Cox proportional hazard models on data from 4 293 544 individuals (99% of Norwegian adults), we estimated overall, age-, and product-specific vaccine effectiveness against SARS-CoV-2 infection, hospitalisation, ICU admission and death in Norway, using data from national registries. Vaccine status was included as time-dependent variable and we adjusted for sex, pre-existing medical conditions, country of birth, county of residence, and crowded living conditions. Results: Adjusted vaccine effectiveness among fully vaccinated is 72.1% (71.2-73.0) against SARS-CoV-2 infection, 92.9% (91.2-94.2) against hospitalisation, 95.5% (92.6-97.2) against ICU admission, and 88.0% (82.5-91.8) against death. Among partially vaccinated, the effectiveness is 24.3% (22.3-26-2) against infection and 82.7% (77.7-86.6) against hospitalisation. Vaccine effectiveness against infection is 84.7% (83.1-86.1) for heterologous mRNA vaccine regimens, 78.3% (76.8-79.7) for Spikevax (Moderna; mRNA-1273), 69.7% (68.6-70.8) for Comirnaty (Pfizer/BioNTech; BNT162b2), and 60.7% (57.5-63.6) for Vaxzevria (AstraZeneca; ChAdOx nCoV-19; AZD1222) with a mRNA dose among fully vaccinated. Conclusion: We demonstrate good protection against SARS-CoV-2 infection and severe disease in fully vaccinated, including heterologous vaccine regimens, which could facilitate rapid immunization. Partially vaccinated were less likely to get severe disease than unvaccinated, though protection against infection was not as high, which could be essential in making vaccine prioritisation policies especially when availability is limited.
Subject(s)
COVID-19 , DeathABSTRACT
COVID-19 has caused high morbidity and mortality in long-term care facilities (LTCFs) worldwide. We estimated vaccine effectiveness (VE) among residents and health care workers (HCWs) in LTCFs using Cox regressions. The VE against SARS-CoV-2 infection was 81.5 (95%CI: 75.3 - 86.1 82.7%) and 81.4% (95%CI: 74.5-86.4%) [≥] 7 days after 2nd vaccine dose among residents and staff respectively. The VE against COVID-19 associated death was 93.1% among residents, no hospitalisations occurred among HCW [≥]7 days after 2nd dose.
Subject(s)
COVID-19ABSTRACT
The COVID-19 response in most countries depends on testing, isolation, contact tracing, and quarantine, which is labor- and time consuming. Therefore, several countries worldwide launched Bluetooth based apps as supplemental tools. We evaluated the new Norwegian GAEN (Google Apple Exposure Notification) based contact tracing app 'Smittestopp' under two relevant simulated scenarios, namely standing in a queue and riding public transport. We compared two configurations (C1: 58/63 dBm; C2: 58/68 dBm) with multiple weights (1.0-2.5) and time thresholds (10-15 min), by calculating notification rates among close contacts ([≤]2 meters, [≥]15 min) and other non-close contacts. In addition, we estimated the effect of using different operating systems and locations of phone (hand/pocket) using Chi2. C2 resulted in significantly higher notification rates than C1 (p-value 0.05 - 0.005). The optimal setting resulted in notifications among 80% of close contacts and 34% of other contacts, using C2 with weights of 2.0 for the low and 1.5 for the middle bucket with a 13-minutes time threshold. Among other contacts, the notification rate was 67% among those [≤]2 meters for <15 minutes compared to 19% among those >2 meters (p=0.004). Significantly (p-values 0.046 - 0.001) lower notification rates were observed when using the iOS operating systems or carrying the phone in the pocket instead of in the hand. This study highlights the importance of testing and optimizing the performance of contact tracing apps under 'real life' conditions to optimized configuration for identifying close contacts.