Relative effectiveness of a 2nd booster dose of COVID-19 mRNA vaccine up to four months post administration in individuals aged 80 years or more in Italy. A retrospective matched cohort study

Several countries started a 2nd booster COVID-19 vaccination campaign targeting the elderly population, but evidence around its effectiveness is still scarce. This study aims to estimate the relative effectiveness of a 2nd booster dose of COVID-19 mRNA vaccine in the population aged >= 80 years in Italy, during predominant circulation of the Omicron BA.2 and BA.5 subvariants. We linked routine data from the national vaccination registry and the COVID-19 surveillance system. On each day between 11 April and 6 August 2022, we matched 1:1, according to several demographic and clinical characteristics, individuals who received the 2nd booster vaccine dose with individuals who received the 1st booster vaccine dose at least 120 days earlier. We used the Kaplan-Meier method to compare the risks of SARS-CoV-2 infection and severe COVID-19 (hospitalisation or death) between the two groups, calculating the relative vaccine effectiveness (RVE) as (1 - risk ratio)X100. Based on the analysis of 831,555 matched pairs, we found that a 2nd booster dose of mRNA vaccine, 14-118 days post administration, was moderately effective in preventing SARS-CoV-2 infection compared to a 1st booster dose administered at least 120 days earlier [14.3 %, 95 % confidence interval (CI): 2.2-20.2]. RVE decreased from 28.5 % (95 % CI: 24.7-32.1) in the time-interval 14-28 days to 7.6 % (95 % CI: -14.1 to 18.3) in the time-interval 56-118 days. However, RVE against severe COVID19 was higher (34.0 %, 95 % CI: 23.4-42.7), decreasing from 43.2 % (95 % CI: 30.6-54.9) to 27.2 % (95 % CI: 8.3-42.9) over the same time span. Although RVE against SARS-CoV-2 infection was much reduced 2-4 months after a 2nd booster dose, RVE against severe COVID-19 was about 30 %, even during prevalent circulation of the Omicron BA.5 subvariant. The cost-benefit of a 3rd booster dose for the elderly people who received the 2nd booster dose at least four months earlier should be carefully evaluated

Impatto della vaccinazione e della pregressa diagnosi sul rischio di infezione e di malattia severa associata a SARS-CoV-2. Un’analisi dei casi diagnosticati nel mese di ottobre 2022

In Italia, l’epidemia di infezioni da SARS-CoV-2 nel corso del 2022 è stata influenzata dalla predominanza della variante Omicron, caratterizzata da alta trasmissibilità, e dalla progressiva eliminazione di quasi tutte le misure non farmacologiche di prevenzione. La combinazione di questi due elementi ha determinato una notevole circolazione virale di SARS-CoV-2 con oltre 24,5 milioni di casi da inizio epidemia. Dato l’alto numero di persone che ha superato almeno una infezione da SARS-CoV-2 e l’alta copertura vaccinale nella popolazione è necessario stimare il ruolo protettivo dell’immunità associata sia al vaccino che all’infezione pregressa nel prevenire l’infezione e la malattia severa da COVID-19. Il presente rapporto fornisce una stima del rischio di infezione e di malattia grave, per il mese di ottobre 2022, sulla base della vaccinazione e della precedente infezione. La massima protezione contro la diagnosi di infezione da SARS-CoV-2 e la malattia severa si realizza attraverso una immunità ibrida (l’effetto combinato della vaccinazione e della pregressa infezione) mentre livelli di rischio più alto si riscontrano sempre tra le persone non vaccinate e senza una precedente diagnosi di infezione. A parità di fascia di età e di pregressa infezione, si osserva una tendenza alla riduzione del rischio di malattia severa associata alla vaccinazione, in particolare se recente

Effectiveness of BNT162b2 vaccine against SARS-CoV-2 infection and severe COVID-19 in children aged 5-11 years in Italy. A retrospective analysis of January-April, 2022

Background By April 13, 2022, more than 4 months after the approval of BNT162b2 (Pfizer-BioNTech) for children, less than 40% of 5-11-year-olds in Italy had been vaccinated against COVID-19. Estimating how effective vaccination is in 5-11-year-olds in the current epidemiological context dominated by the omicron variant (B.1.1.529) is important to inform public health bodies in defining vaccination policies and strategies. Methods In this retrospective population analysis, we assessed vaccine effectiveness against SARS-CoV-2 infection and severe COVID-19, defined as an infection leading to hospitalisation or death, by linking the national COVID-19 surveillance system and the national vaccination registry. All Italian children aged 5-11 years without a previous diagnosis of infection were eligible for inclusion and were followed up from Jan 17 to April 13, 2022. All children with inconsistent vaccination data, diagnosed with SARS-CoV-2 infection before the start date of the study or without information on the municipality of residence were excluded from the analysis. With unvaccinated children as the reference group, we estimated vaccine effectiveness in those who were partly vaccinated (one dose) and those who were fully vaccinated (two doses). Findings By April 13, 2022, 1 063 035 (35middot8%) of the 2 965 918 children aged 5-11 years included in the study had received two doses of the vaccine, 134 386 (4middot5%) children had received one dose only, and 1 768 497 (59middot6%) were unvaccinated. During the study period, 766 756 cases of SARS-CoV-2 infection and 644 cases of severe COVID-19 (627 hospitalisations, 15 admissions to intensive care units, and two deaths) were notified. Overall, vaccine effectiveness in the fully vaccinated group was 29middot4% (95% CI 28middot5-30middot2) against SARS-CoV-2 infection and 41middot1% (22middot2-55middot4) against severe COVID-19, whereas vaccine effectiveness in the partly vaccinated group was 27middot4% (26middot4-28middot4) against SARS-CoV-2 infection and 38middot1% (20middot9-51middot5) against severe COVID-19. Vaccine effectiveness against infection peaked at 38middot7% (37middot7-39middot7) at 0-14 days after full vaccination and decreased to 21middot2% (19middot7-22middot7) at 43-84 days after full vaccination. Interpretation Vaccination against COVID-19 in children aged 5-11 years in Italy showed a lower effectiveness in preventing SARS-CoV-2 infection and severe COVID-19 than in individuals aged 12 years and older. Effectiveness against infection appears to decrease after completion of the current primary vaccination cycle. Copyright (c) 2022 Elsevier Ltd. All rights reserved

Effectiveness of an mRNA vaccine booster dose against SARS-CoV-2 infection and severe COVID-19 in persons aged ≥60 years and other high-risk groups during predominant circulation of the delta variant in Italy, 19 July to 12 December 2021

29siBackground Consolidated information on the effectiveness of COVID-19 booster vaccination in Europe are scarce. Research design and methods We assessed the effectiveness of a booster dose of an mRNA vaccine against any SARS-CoV-2 infection (symptomatic or asymptomatic) and severe COVID-19 (hospitalization or death) after over two months from administration among priority target groups (n = 18,524,568) during predominant circulation of the Delta variant in Italy (July-December 2021). Results Vaccine effectiveness (VE) against SARS-CoV-2 infection and, to a lesser extent, against severe COVID-19, among people >= 60 years and other high-risk groups (i.e. healthcare workers, residents in long-term-care facilities, and persons with comorbidities or immunocompromised), peaked in the time-interval 3-13 weeks (VE against infection = 67.2%, 95% confidence interval (CI): 62.5-71.3; VE against severe disease = 89.5%, 95% CI: 86.1-92.0) and then declined, waning 26 weeks after full primary vaccination (VE against infection = 12.2%, 95% CI: -4.7-26.4; VE against severe disease = 65.3%, 95% CI: 50.3-75.8). After 3-10 weeks from the administration of a booster dose, VE against infection and severe disease increased to 76.1% (95% CI: 70.4-80.7) and 93.0% (95% CI: 90.2-95.0), respectively. Conclusions These results support the ongoing vaccination campaign in Italy, where the administration of a booster dose four months after completion of primary vaccination is recommended.nonenoneFabiani, Massimo; Puopolo, Maria; Filia, Antonietta; Sacco, Chiara; Mateo-Urdiales, Alberto; Spila Alegiani, Stefania; Del Manso, Martina; D’Ancona, Fortunato; Vescio, Fenicia; Bressi, Marco; Petrone, Daniele; Spuri, Matteo; Rota, Maria Cristina; Massari, Marco; Da Cas, Roberto; Morciano, Cristina; Stefanelli, Paola; Bella, Antonino; Tallon, Marco; Proietti, Valeria; Siddu, Andrea; Battilomo, Serena; Palamara, Anna Teresa; Popoli, Patrizia; Brusaferro, Silvio; Rezza, Giovanni; Riccardo, Flavia; Menniti Ippolito, Francesca; Pezzotti, PatrizioFabiani, Massimo; Puopolo, Maria; Filia, Antonietta; Sacco, Chiara; Mateo-Urdiales, Alberto; Spila Alegiani, Stefania; Del Manso, Martina; D’Ancona, Fortunato; Vescio, Fenicia; Bressi, Marco; Petrone, Daniele; Spuri, Matteo; Rota, Maria Cristina; Massari, Marco; Da Cas, Roberto; Morciano, Cristina; Stefanelli, Paola; Bella, Antonino; Tallon, Marco; Proietti, Valeria; Siddu, Andrea; Battilomo, Serena; Palamara, Anna Teresa; Popoli, Patrizia; Brusaferro, Silvio; Rezza, Giovanni; Riccardo, Flavia; Menniti Ippolito, Francesca; Pezzotti, Patrizi