Reactogenicity to the mRNA-1273 Booster According to Previous mRNA COVID-19 Vaccination.

The objective of this study was to assess the local and systemic adverse reactions after the administration of a COVID-19 mRNA-1273 booster between December 2021 and February 2022 by comparing the type of mRNA vaccine used as primary series (mRNA-1273 or BNT162b2) and homologous versus heterologous booster in health care workers (HCW). A cross-sectional study was performed in HCW at a tertiary hospital in Barcelona, Spain. A total of 17% of booster recipients responded to the questionnaire. The frequency of reactogenicity after the mRNA-1273 booster (88.5%) was similar to the mRNA-1273 primary doses (85.8%), and higher than the BNT162b2 primary doses (71.1%). The reactogenicity was similar after receiving a heterologous booster compared to a homologous booster (88.0% vs. 90.2%, p = 0.3), and no statistically significant differences were identified in any local or systemic reactions. A higher frequency of medical leave was identified in the homologous booster dose group vs. the heterologous booster dose group (AOR 1.45; 95% CI: 1.00-2.07; p = 0.045). Our findings could be helpful in improving vaccine confidence toward heterologous combinations in the general population and in health care workers.

Vaccine hesitancy among paediatric nurses: Prevalence and associated factors.

OBJECTIVE: This study describes the prevalence of vaccine hesitancy associated with the Catalan systematic childhood vaccination calendar and some related psychosocial determinants among paediatric primary care nurses in Barcelona (Spain). METHODS: Cross-sectional descriptive study. In 2017 we invited the paediatric nurses (N = 165) working in Barcelona public primary health centres with paediatric departments (N = 41) to participate. They answered a questionnaire with sociodemographic and behavioural variables: severity and perceived probability of contracting the diseases of the vaccines in the vaccination schedule; safety and protection offered by each vaccine; and beliefs, social norms, and knowledge about vaccines. Outcome variable was vaccine hesitancy, dichotomized into not hesitant (nurses who would vaccinate their own offspring), and hesitant (including those who would not vaccinate them, those who had doubts and those who would delay the administration of one or more vaccines). We performed bivariate analysis and adjusted logistic regression models. RESULTS: 83% of paediatric nurses (N = 137) agreed to participate. 67.9% had the intention to vaccinate their children of all the vaccines in the systematic schedule. 32.1% of nurses experienced vaccine hesitancy, especially about the HPV (21.9%) and varicella (17.5%) vaccines. The multivariate analysis suggests associations between hesitancy and low perception of the severity of whooping cough (aOR: 3.88; 95%CI:1.32-11.4), low perception of safety of the HPV vaccine (aOR:8.5;95%CI:1.24-57.8), the belief that vaccines are administered too early (aOR:6.09;95%CI:1.98-18.8), and not having children (aOR:4.05;95%CI:1.22-13.3). CONCLUSIONS: Although most paediatric nurses had the intention to vaccinate their own children, almost one-third reported some kind of vaccine hesitancy, mainly related to doubts about HPV and varicella vaccines, as well as some misconceptions. These factors should be addressed to enhance nurses' fundamental role in promoting vaccination to families.

Local and Systemic Adverse Reactions to mRNA COVID-19 Vaccines Comparing Two Vaccine Types and Occurrence of Previous COVID-19 Infection.

The aim of this study was to assess adverse reactions to COVID-19 vaccines, comparing the BNT162b2 or the mRNA-1273 COVID-19 vaccines and the presence and seriousness of a previous COVID-19 infection. We conducted a cross-sectional online survey of vaccinated healthcare workers at a tertiary hospital in Barcelona (Spain). Thirty-eight percent of vaccine recipients responded to the questionnaire. We compared the prevalence of adverse reactions by vaccine type and history of COVID-19 infections. A total of 2373 respondents had received the BNT162b2 vaccine, and 506 the mRNA-1273 vaccine. The prevalence of at least one adverse reaction with doses 1 and 2 was 41% and 70%, respectively, in the BNT162b2 group, and 60% and 92% in the mRNA-1273 group (p < 0.001). The BNT162b2 group reported less prevalence of all adverse reactions. Need for medical leave was significantly more frequent among the mRNA-1273 group (12% versus 4.6% p < 0.001). Interestingly, respondents with a history of allergies or chronic illnesses did not report more adverse reactions. The frequency of adverse reactions with dose 2 was 96% (95% CI 88-100%) for those with a history of COVID-19 related hospitalization, and 86% (95% CI 83-89%) for those with mild or moderate symptomatic COVID-19, significantly higher than for participants with no history of COVID-19 infections (67%, 95% CI 65-69%). Our results could help inform vaccine recipients of the probability of their having adverse reactions to COVID-19 vaccines.

Effectiveness of varicella vaccines as postexposure prophylaxis.

BACKGROUND: Although chickenpox is usually a mild disease, it is not always free of complications, especially in adolescents and adults. Previous studies of postexposure prophylaxis conducted with experimental vaccines showed the vaccine to be highly effective if administered in the first 3 to 5 days after exposure. However, studies carried out with commercialized vaccines yielded discordant results. The aim of the present study was to assess the effectiveness of currently available varicella vaccines as postexposure prophylaxis. METHODS: We conducted a prospective cohort study. Patients susceptible to chickenpox consulting at the Preventive Medicine Department of the Vall d'Hebron Hospital after household exposure to a case of chickenpox were included. Postexposure prophylaxis with varicella vaccine was administered within the first 5 days after contact. Subjects were interviewed by telephone between 4 and 8 weeks after vaccination to ascertain whether chickenpox had appeared and, if so, its severity. The effectiveness of the vaccine in preventing and attenuating the disease was calculated with a confidence interval of 95%. RESULTS: Sixty-seven subjects were included in the study. Effectiveness of the varicella vaccine in preventing any type of disease was 62.3% (CI 95%: 47.8-74.9) and 79.4% (CI 95%: 66.4-88.9) in preventing moderate and severe disease. No statistically significant differences were found when effectiveness was compared according to sex, age, or days elapsed since exposure. CONCLUSIONS: Administration of varicella vaccines within the first 5 days postexposure is effective in preventing chickenpox and in attenuating the illness.