Anti-Sars-CoV-2 vaccination campaign in children aged 5-11 years: the experience of a mass vaccination center in the city of Milan.

BACKGROUND AND AIM: After the approval of the anti-Sars-CoV-2 vaccines for the pediatric population, it is necessary to encourage the immunization of children aged 5-11 years, as this can reduce intergenerational transmission. Therefore, this goal has become a priority for the COVID 19 vaccination campaign in Italy. In the city of Milan, the mass vaccination center (MVC) Fiera Milano City, previously settled for general population, became the main site to host pediatric vaccinations. The center was consequently remodeled to ensure a suitable space for children. This paper provides an overview on the organization strategy implemented by Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico. The modular structure and the wide surface available in the center allowed the administration of hundreds of vaccines per day, especially in the first opening phase. METHODS: All the data for the entire period of activity of Fiera MCV, from December 16th 2021 to February 20th 2022, were analyzed using descriptive statistics. RESULTS: During the entire period of activity, from 16 December 2021 to 20 February 2022, 23% of the population in the province of Milan aged 5-11 years has been reached and vaccinated with at least one shot of vaccine in this center. CONCLUSIONS: Despite an enthusiastic response in the first weeks of the campaign, a progressive reduction in vaccination adherence was observed, maybe due to the absence of restrictive measures for unvaccinated children in Italy.

Balancing Benefits and Harms of COVID-19 Vaccines: Lessons from the Ongoing Mass Vaccination Campaign in Lombardy, Italy.

Background. Limited evidence exists on the balance between the benefits and harms of the COVID-19 vaccines. The aim of this study is to compare the benefits and safety of mRNA-based (Pfizer-BioNTech and Moderna) and adenovirus-vectored (Oxford-AstraZeneca) vaccines in subpopulations defined by age and sex. Methods. All citizens who are newly vaccinated from 27 December 2020 to 3 May 2021 are matched to unvaccinated controls according to age, sex, and vaccination date. Study outcomes include the events that are expected to be avoided by vaccination (i.e., hospitalization and death from COVID-19) and those that might be increased after vaccine inoculation (i.e., venous thromboembolism). The incidence rate ratios (IRR) of vaccinated and unvaccinated citizens are separately estimated within strata of sex, age category and vaccine type. When suitable, number needed to treat (NNT) and number needed to harm (NNH) are calculated to evaluate the balance between the benefits and harm of vaccines within each sex and age category. Results. In total, 2,351,883 citizens are included because they received at least one dose of vaccine (755,557 Oxford-AstraZeneca and 1,596,326 Pfizer/Moderna). A reduced incidence of COVID-19-related outcomes is observed with a lowered incidence rate ranging from 55% to 89% and NNT values ranging from 296 to 3977. Evidence of an augmented incidence of harm-related outcomes is observed only for women aged <50 years within 28 days after Oxford-AstraZeneca (being the corresponding adjusted IRR of 2.4, 95% CI 1.1-5.6, and NNH value of 23,207, 95% CI 10,274-89,707). Conclusions. A favourable balance between benefits and harms is observed in the current study, even among younger women who received Oxford-AstraZeneca.

Protective action of natural and induced immunization against the occurrence of delta or alpha variants of SARS-CoV-2 infection: a test-negative case-control study.

BACKGROUND: The evolution of SARS-CoV-2 has led to the emergence of several new variants, and few data are available on the impact of vaccination on SARS-CoV-2 variants. We aimed to assess the association between natural (previous infection) and induced (partial or complete vaccination) exposure to SARS-CoV-2 and the onset of new infection supported by the delta variant, and of comparing it with that supported by alpha. METHODS: We performed a test-negative case-control study, by linking population-based registries of confirmed diagnoses of infection with SARS-CoV-2, vaccinations against Covid-19 and healthcare utilization databases of the Italian Lombardy Region. Four hundred ninety-six persons who between 27 December 2020 and 16 July 2021 had an infection by the delta variant were 1:1 matched with citizens affected by alphavariant and 1:10 matched with persons who had a negative molecular test, according to gender, age and date of molecular ascertainment. We used a conditional logistic regression for estimating relative risk reduction of either variants associated with natural and/or induced immunization and corresponding 95% confidence interval (CI). RESULTS: Previous infection was associated with 91% (95% CI 85% to 95%) reduced relative risk of reinfection, without evidence of significant differences between delta and alpha cases (p=0.547). Significant lower vaccinal protection against delta than alpha variant infection was observed with reduced relative risk associated with partial vaccination respectively of 29% (7% to 45%), and 62% (48% to 71%) (p=0.001), and with complete vaccination respectively of 75% (66% to 82%) and 90% (85% to 94%) (p=0.003). CONCLUSIONS: Lower protection towards infections caused by the delta variant with respect to alpha variant was noticed, even after the completion of the vaccination cycle. This finding would support efforts to maximize both vaccine uptake with two doses and fulfilment with individual protection measures, especially as the delta variant is rampant worldwide presently.