Impact of booster vaccination on COVID-19 outcomes in Portuguese population aged 80 or more years old

Abstract Background Vaccination is essential to control SARS-CoV-2 transmission and complications. The study aimed to estimate the number of SARS-CoV-2 infections, COVID-19 hospitalizations and deaths averted by booster vaccination in Portuguese population aged 80 or more years old. Methods We developed an ecological study for the period of the Omicron variant of concern predominance (week 2 to week 16, 2022). Data on vaccine coverage and effectiveness, and number of events of different severity reported to the national COVID-19 surveillance system were used to estimate the number of averted events, prevented fraction and number needed to vaccinate. Uncertainty intervals (UI) were obtained using Monte Carlo simulations. Results By week 2 2022, vaccination coverage in the target population reached 91.2%. Booster vaccine effectiveness was 4.1% (CI95%: -0.1 to 9.0), 87.5% (CI95%: 84.9 to 89.7) and 83.2 (CI95%: 80.3 to 85.7) against infection, hospitalization and death, respectively. During the study period, 70862 SARS-CoV-2 infections, 2697 COVID-19 hospitalizations and 2106 deaths were reported. Booster vaccination averted 2731 (UI95%: -298 to 5838) infections, 10629 (UI95%: 9173 to 12127) hospitalizations and 6608 (UI95%: 5725 to 7546) COVID-19 related deaths among individuals aged 80 years or more resident in Portugal. Prevented fractions were 3.7% (UI95%: 0 to 7.6%), 79.7% (UI95%: 77.3 to 81.7%) and 75.8% (UI95%: 73.2 to 78.1%), respectively. It would require to vaccinate 59 individuals (UI95%: 52 to 69) to prevent one hospitalization and 94 individuals (UI95%: 82 to 109) to prevent one death in the target population. Conclusions The booster vaccination strategy had considerable impact on preventing severe outcomes in the Portuguese population aged 80 and more years old. Key messages • High vaccine coverage combined with high vaccine effectiveness resulted in considerable reduction of severe COVID-19 outcomes. • Information on number of outcomes of different severity levels averted by COVID-19 booster vaccination allows to strength public health communication.


Background:
Pregnant and breastfeeding women are at an increased risk of severe illness from COVID-19 compared to people who are not pregnant. Therefore, the CDC recommends COVID-19 vaccination for women who are pregnant, breastfeeding, and trying to become pregnant or who may become pregnant in the future. Despite this, low vaccination coverages are reported in this population sub-group. The purpose of this study is to estimate the proportion of pregnant and breastfeeding women expressing hesitation to the COVID-19 vaccine worldwide. Determinants of vaccine compliance and options suggestedto address vaccine hesitancy were also analyzed.

Methods:
Forty-six studies were included in the meta-analysis and systematic review, selected from scientific articles available in the MEDLINE/PubMed, Google Scholar, and Scopus databases between January 1, 2020 and February 6, 2022. The following terms were used for the search strategy: (adherence OR hesitancy OR compliance OR attitude) AND (covid Ã OR SARS Ã ) AND (vaccin Ã OR immun Ã ) AND (pregnan Ã OR postpartum OR breastfeeding OR lactating).

Results:
The vaccine hesitation rate was 48.4% (95%CI = 43.4-53.4%). In a sub analysis by study period, the pooled prevalence of vaccine hesitation was 40.0% (95%CI = 31.6-46.6%) considering surveys administered in 2020, 58.0% (95%CI = 48.9-66.9%) considering surveys administered in the first semester of 2021, and 38.1% (95%CI = 25.9-51.2%) considering surveys administered in the second semester of 2021. The main reasons for vaccine hesitation were lack of information about vaccination, opinion that the vaccine is unsafe, and fear of adverse events for both mother and fetus/child.

Conclusions:
In order to achieve high vaccination coverage, a multifactorial approach is needed, requiring major social, scientific, and health efforts. The success of the vaccination campaign in this population depends on the capillarity and consistency of the interventions implemented.

Key messages:
Vaccine hesitancy can be a determining factor in the success (or otherwise) of the anti-COVID-19 immunization campaign. Vaccine hesitancy in pregnant and breastfeeding women is a genuine public health concern worldwide. Background: Vaccination is essential to control SARS-CoV-2 transmission and complications. The study aimed to estimate the number of SARS-CoV-2 infections, COVID-19 hospitalizations and deaths averted by booster vaccination in Portuguese population aged 80 or more years old.

Methods:
We developed an ecological study for the period of the Omicron variant of concern predominance (week 2 to week 16, 2022

Results:
The COVIMO study indicates an achievable vaccination compliance rate of 83.9% among 12-59-year-olds and 94.8% among those ! 60-year-olds. Maximum incidence or ICU utilization during observation period decreases from 385 to 61 and 6220 to 2800, respectively, with an increase in vaccination coverage from 65% to 95% of 12-59-year-olds, 90% vaccination rate among ! 60-year-olds, compared to pre-pandemic reduced contact behaviour in summer and reduction of contacts as case numbers increase.

Conclusions:
The vaccination campaign should be continued at high intensity until at least 85% of 12-59-year-olds or 90%

Introduction:
Vaccination is the primary pharmacological measure to reduce SARS-CoV-2 transmission and its complications. Timely information on vaccines effectiveness in a context of novel variants of concern (VOC) emergence is essential for public health policies. This study aimed to provide a measure of comparative vaccine effectiveness between Omicron (BA.1) and Delta (B.1.627.2) VOC according to vaccination exposure (complete primary regimen or booster dose) for Portuguese population aged 12 or more years old using routinely collected data from electronic health records.

Methods:
We used a case-case study design linking national electronic vaccination registry and surveillance data on 13,134 SARS-CoV-2 RT-PCR laboratory-confirmed cases notified in Portugal during weeks 49-51 of 2021. Notified cases were classified as Omicron or Delta based on whole-genome sequencing or S-gene Target Failure (SGTF) status using the RT-PCR TaqPath TM Covid 19 CE IVD Kit (Thermo Scientific TM ) assay. The odds of vaccination was compared between Omicron cases and Delta cases using logistic regression adjusted for age group, sex, region and week of diagnosis and laboratory of origin.

Results:
The odds of vaccination were higher in laboratory-confirmed cases infected by Omicron (BA.

Conclusions:
We found significantly higher odds of vaccination in Omicron cases compared to Delta, suggesting lower effectiveness of the primary vaccination and the booster dose in preventing infections by Omicron. Case-case study design has proven to be feasible approach to rapidly compare vaccine effectiveness between VOC in context of novel VOC emergence to timely inform public health stakeholders. Key messages: Reduction of vaccine-induced protection against SARS-COV-2 infection with the Omicron compared to Delta after primary and booster vaccination. Continuous monitoring of COVID-19 vaccine effectiveness is essential to support public health policies in context of novel VOC emergence.