Age-Dependent Effects of COVID-19 Vaccine and of Healthcare Burden on COVID-19 Deaths,Tokyo, Japan

COVID-19 vaccine effectiveness against death in Japan remains unknown. Furthermore, although evidence indicates that healthcare capacity influences case-fatality risk (CFR), it remains unknown whether this relationship is mediated by age. With a modeling study, we analyzed daily COVID-19 cases and deaths during January–August 2021 by using Tokyo surveillance data to jointly estimate COVID-19 vaccine effectiveness against death and age-specific CFR. We also examined daily healthcare operations to determine the association between healthcare burden and age-specific CFR. Among fully vaccinated patients, vaccine effectiveness against death was 88.6% among patients 60–69 years of age, 83.9% among patients 70–79 years of age, 83.5% among patients 80–89 years of age, and 77.7% among patients >90 years of age. A positive association of several indicators of healthcare burden with CFR among patients >70 years of age suggested an age-dependent effect of healthcare burden on CFR in Japan.     

Socioeconomic Inequalities in COVID-19 Vaccination and Infection in Adults,Catalonia, Spain

Evidence on the impact of the COVID-19 vaccine rollout on socioeconomic COVID-19–related inequalities is scarce. We analyzed associations between socioeconomic deprivation index (SDI) and COVID-19 vaccination, infection, and hospitalization before and after vaccine rollout in Catalonia, Spain. We conducted a population-based cohort study during September 2020–June 2021 that comprised 2,297,146 adults >40 years of age. We estimated odds ratio of nonvaccination and hazard ratios (HRs) of infection and hospitalization by SDI quintile relative to the least deprived quintile, Q1. Six months after rollout, vaccination coverage differed by SDI quintile in working-age (40–64 years) persons: 81% for Q1, 71% for Q5. Before rollout, we found a pattern of increased HR of infection and hospitalization with deprivation among working-age and retirement-age (>65 years) persons. After rollout, infection inequalities decreased in both age groups, whereas hospitalization inequalities decreased among retirement-age persons. Our findings suggest that mass vaccination reduced socioeconomic COVID-19–related inequalities.     

Association between COVID-19 vaccination status,time elapsed since the last vaccine dose,morbidity, and absenteeism among healthcare personnel: A prospective,multicenter study

AimWe assessed the impact of COVID-19 vaccination status and time elapsed since the last vaccine dose on morbidity and absenteeism among healthcare personnel (HCP) in the context of a mandatory vaccination policy.MethodsWe followed 7592 HCP from November 15, 2021 through April 17, 2022. Full COVID-19 vaccination was defined as a primary vaccination series plus a booster dose at least six months later.ResultsThere were 6496 (85.6 %) fully vaccinated, 953 (12.5 %) not fully vaccinated, and 143 (1.9 %) unvaccinated HCP. A total of 2182 absenteeism episodes occurred. Of 2088 absenteeism episodes among vaccinated HCP with known vaccination status, 1971 (94.4 %) concerned fully vaccinated and 117 (5.6 %) not fully vaccinated. Fully vaccinated HCP had 1.6 fewer days of absence compared to those not fully vaccinated (8.1 versus 9.7; p-value < 0.001). Multivariable regression analyses showed that full vaccination was associated with shorter absenteeism compared to not full vaccination (OR: 0.56; 95 % CI: 0.36–0.87; p-value = 0.01). Compared to a history of ≤ 17.1 weeks since the last dose, a history of > 17.1 weeks since the last dose was associated with longer absenteeism (OR: 1.22, 95 % CI:1.02–1.46; p-value = 0.026) and increased risk for febrile episode (OR: 1.33; 95 % CI: 1.09–1.63; p-value = 0.004), influenza-like illness (OR: 1.53, 95 % CI: 1.02–2.30; p-value = 0.038), and COVID-19 (OR: 1.72; 95 % CI: 1.24–2.39; p-value = 0.001).ConclusionsThe COVID-19 pandemic continues to impose a considerable impact on HCP. The administration of a vaccine dose in less than four months before significantly protected against COVID-19 and absenteeism duration, irrespective of COVID-19 vaccination status. Defining the optimal timing of boosters is imperative.     

Direct and Indirect Effectiveness of mRNA Vaccination against Severe Acute Respiratory Syndrome Coronavirus 2 in Long-Term Care Facilities,Spain

We conducted a registries-based cohort study of long-term care facility residents >65 years of age offered vaccination against severe acute respiratory syndrome coronavirus 2 before March 10, 2021, in Spain. Risk for infection in vaccinated and nonvaccinated persons was compared with risk in the same persons in a period before the vaccination campaign, adjusted by daily-varying incidence and reproduction number. We selected 299,209 persons; 99.0% had >1 dose, 92.6% had 2 doses, and 99.8% of vaccines were Pfizer/BioNTech (BNT162b2). For vaccinated persons with no previous infection, vaccine effectiveness was 81.8% (95% CI 81.0%–82.7%), and 11.6 (95% CI 11.3–11.9) cases were prevented per 10,000 vaccinated/day. In those with previous infection, effectiveness was 56.8% (95% CI 47.1%–67.7%). In nonvaccinated residents with no previous infection, risk decreased by up to 81.4% (95% CI 73.3%–90.3%). Our results confirm vaccine effectiveness in this population and suggest indirect protection in nonvaccinated persons.     

Receipt of COVID-19 and seasonal influenza vaccines in California (USA) during the 2021–2022 influenza season

BackgroundDespite lower circulation of influenza virus throughout 2020–2022 during the COVID-19 pandemic, seasonal influenza vaccination has remained a primary tool to reduce influenza-associated illness and death. The relationship between the decision to receive a COVID-19 vaccine and/or an influenza vaccine is not well understood.MethodsWe assessed predictors of receipt of 2021–2022 influenza vaccine in a secondary analysis of data from a case-control study enrolling individuals who received SARS-CoV-2 testing. We used mixed effects logistic regression to estimate factors associated with receipt of seasonal influenza vaccine. We also constructed multinomial adjusted marginal probability models of being vaccinated for COVID-19 only, seasonal influenza only, or both as compared with receipt of neither vaccination.ResultsAmong 1261 eligible participants recruited between 22 October 2021–22 June 2022, 43% (545) were vaccinated with both seasonal influenza vaccine and >1 dose of a COVID-19 vaccine, 34% (426) received >1 dose of a COVID-19 vaccine only, 4% (49) received seasonal influenza vaccine only, and 19% (241) received neither vaccine. Receipt of >1 COVID-19 vaccine dose was associated with seasonal influenza vaccination (adjusted odds ratio [aOR]: 3.72; 95% confidence interval [CI]: 2.15–6.43); this association was stronger among participants receiving >1 COVID-19 booster dose (aOR = 16.50 [10.10–26.97]). Compared with participants testing negative for SARS- CoV-2 infection, participants testing positive had lower odds of receipt of 2021-2022 seasonal influenza vaccine (aOR = 0.64 [0.50–0.82]).ConclusionsRecipients of a COVID-19 vaccine were more likely to receive seasonal influenza vaccine during the 2021–2022 season. Factors associated with individuals’ likelihood of receiving COVID-19 and seasonal influenza vaccines will be important to account for in future studies of vaccine effectiveness against both conditions. Participants who tested positive for SARS-CoV-2 in our sample were less likely to have received seasonal influenza vaccine, suggesting an opportunity to offer influenza vaccination before or after a COVID-19 diagnosis.     

Patients with history of covid-19 had more side effects after the first dose of covid-19 vaccine

IntroductionCOVID-19 vaccination seems to be the most pertinent pharmacologic public health measure to control the pandemic. Reactogenicity symptoms were frequent in vaccine recipients mostly mild to moderate and commonly reported after the second dose. However, there is a lack of data in patients with a previous diagnosis of Covid-19.MethodsWe analysed side effects of 311 patients after the first dose of Pfizer-BioNTech COVID-19 vaccine, in a french university hospital. We compared patients with COVID-19 history to naive individuals. All the data collected are based on self-reported, including COVID-19 exposure status.ResultsOverall, 229 (74%) patients reported at least one side effect. Among participants with history of Covid-19, 95% reported at least one adverse event versus 70% in naive patients (p < 0.01). However, symptom intensity was not different between the 2 groups.ConclusionVaccine recipients with prior COVID-19 reported more, but no more serious, side effects than naive participants.     

SARS-CoV-2 infection: efficacy of extensive vaccination of the healthcare workforce in a large Italian hospital

Background:A prospective observational study involved 13,787 Health Care Workers (HCWs) of a large hospital to assess the effectiveness of a SARS-CoV-2 mRNA vaccine.Methods:The daily incidence of infections was estimated from 1st October 2020 to 30th April 2021 and compared with that of the province of Turin (2.26 million). In the middle of this period, a mass vaccination began among HCW, and its effect was assessed.Results:In the first half-period, 1,163 positive HCWs were observed, the average daily incidence rate per 100,000 being 79.58 (± 15.58; 95% CI) compared to 38.54 (± 5.96; 95% CI) in the general population (p<0.001). The vaccination campaign immunized 9,843 HCWs; among them, the average daily incidence was 14.23 (± 2.73; 95% CI) compared to 34.2 (± 2.95; 95% CI) in the province (p<0.001). Among fully vaccinated HCW, 59 cases were observed, giving rise to an incidence of 6.3 (± 2.66; 95% CI) much lower than in the province (p<0.001). In the second half of the observation period, the RR for HCWs compared to the province dropped from 2.07 (1.96 – 2.18; 95% CI; p<0.001) to 0.5 (0.42 – 0.58; 95% CI; p<0.001) and to 0.17 (0.13 – 0.22; 95% CI; p<0.001) for unvaccinated and vaccinated HCWs, respectively. The RR of vaccinate HCW was 0.43 (0.31 – 0.58; 95% CI; p<0.001) compared to unvaccinated. In the second half of the observation period, unvaccinated HCWs had a RR of 0.21 (0.18 – 0.25; 95% CI; p<0.001) as compared to the first one. A linear regression model (R2 = 0.87) showed that every percent increase in vaccinated HCWs lowered daily incidence by 0.94 (0.86 – 1.02; IC 95%; p<0.001). Vaccinated HCWs had a RR of 0.09 (0.07 – 0.12; 95% CI; p<0.001) compared to unvaccinated HCWs, which led to estimated effectiveness of the two-dose vaccine of 91 % (± 3 %; CI 95%) similar to that reported by the manufacturer.     

COVID-19 vaccine coverage disparities in rural and farm children

BackgroundThe risks of severe outcomes associated with SARS-CoV-2 (COVID-19) are elevated in unvaccinated individuals. It remains crucial to understand patterns of COVID-19 vaccination, particularly in younger and remote populations where coverage often lags. This study examined disparities in COVID-19 vaccine coverage in farm children and adolescents.MethodsA cross-sectional analysis was conducted in patients of the Marshfield Clinic Health System (MCHS) in Wisconsin. The sample included children/adolescents age 5–17 years who were eligible for COVID-19 vaccine initiation for ≥ 90 days (as of September 30, 2022), stratified by those who lived vs did not live on a farm. Outcomes included COVID-19 vaccine initiation, series completion, and booster receipt. Multivariable regression was used to examine associations between COVID-19 vaccination and farm, as well as rural and non-rural, residence.ResultsThere were 47,104 individuals (5% farm residents) in the sample. Overall, 33% of participants initiated and 31% completed the COVID-19 vaccine series. After adjustment, farm residence was associated with significantly lower odds of COVID-19 vaccine initiation (aOR [95% CI] = 0.68 [0.61, 0.75], p < 0.001), series completion (aOR = 0.67 [0.60, 0.75], p < 0.001), and booster receipt (aOR = 0.73 [0.61, 0.88], p = 0.001). Secondary analyses found COVID-19 vaccine coverage was lowest in young children who lived on dairy farms.ConclusionsCOVID-19 vaccine coverage is low in north-central Wisconsin children and adolescents. Those who live on farms have significantly lower likelihood of COVID-19 vaccine initiation, series completion, and booster receipt compared to non-farm counterparts. Farm families are an underserved group and require more effective public health interventions designed to prevent COVID-19.     

Hesitation of the Tunisian population to COVID-19 vaccination,and its associated factors

Background: Many people are reluctant to be vaccinated against COVID-19. Aim: To determine the intention to accept COVID19 vaccine and its associated factors among Tunisians. Methods: We conducted a cross-sectional study among Tunisians from December 2020 to January 2021 using an online questionnaire. Factors associated with intention to accept coronavirus vaccine were analysed using multinomial logistic regression. Results: In total, 169 Tunisians participated in our study. The majority were female (85.2%). The mean age was 48.3 ± 11.8 years. Only 33.1% intended to accept to be vaccinated when COVID-19 vaccine will be available in Tunisia and 22.5% were still hesitant. In multinomial logistic regression, participants having high or very high perceived personal risk of COVID-19 infection (aOR:3.257, 95% CI :1.204 – 8.815) were more prone to hesitate to accept COVID-19 vaccine rather than those being willing to accept it. Respondents undergoing seasonal influenza vaccination (aOR: 0.091, 95% CI : 0.019 – 0.433)were less prone to refuse COVID-19 vaccine rather than those being willing to accept it. Young ones aged less than 40 years (aOR: 4.324, 95% CI: 1.180 – 15.843) were more prone to refuse COVID-19 vaccine rather than those being willing to accept it. Conclusion: The acceptance rate of coronavirus vaccination was moderate. Therefore, a good communication and health education at a community level are needed.     

COVID-19 Vaccine Acceptability and Financial Incentives among Unhoused People in Los Angeles County: a Three-Stage Field Survey

Unhoused people have higher COVID-19 mortality and lower vaccine uptake than housed community members. Understanding vaccine hesitancy among unhoused people is key for developing programs that address their unique needs. A three-round, rapid, field-based survey was conducted to describe attitudes toward COVID-19 vaccination. Round 1 assessed vaccine brand preference, round 2 assessed intention to accept a financial incentive for vaccination, and round 3 measured vaccine uptake and assessed reasons for vaccine readiness during implementation of a financial incentive program. A total of 5177 individuals were approached at COVID-19 vaccination events for unhoused people in Los Angeles County from May through November 2021. Analyses included 4949 individuals: 3636 (73.5%) unsheltered and 1313 (26.5%) sheltered. Per self-report, 2008 (40.6%) were already vaccinated, 1732 (35%) wanted to get vaccinated, 359 (7.3%) were not yet ready, and 850 (17.2%) did not want to get vaccinated. Brand preference was evenly split among participants (Moderna 31.0%, J&J 35.5%, either 33.5%, p = 0.74). Interest in a financial incentive differed between those who were not yet ready and those who did not want to get vaccinated (43.2% vs. 16.2%, p < 0.01). After implementing a financial incentive program, 97.4% of participants who indicated interest in vaccination were vaccinated that day; the financial incentive was the most cited reason for vaccine readiness (n = 731, 56%). This study demonstrated the utility of an iterative, field-based assessment for program implementation during the rapidly evolving pandemic. Personal engagement, a variety of brand choices, and financial incentives could be important for improving vaccine uptake among unhoused people.     

Exploring the attitudes,concerns, and knowledge regarding COVID-19 vaccine by the parents of children with rheumatic disease: Cross-sectional online survey

BackgroundVaccination programs are effective strategies in preventing infectious diseases and controlling epidemics. Vaccination against SARS-CoV-2 in children has not yet been approved globally, and it is unclear what attitude families will take when it is approved in children. We aimed to investigate the underlying causes of vaccine acceptance, hesitation, and refusal, as well as concerns about the acceptability of the COVID-19 vaccine by parents of children with rheumatic diseases.MethodsParents of children followed up with a diagnosis of rheumatic disease in the pediatric rheumatology outpatient clinic of a university hospital were included in the study. We applied a closed web-based online survey conducted cross-sectionally and sent to the participants via mobile smartphones.ResultsFor fathers, mothers, and their children, acceptance rates for a COVID-19 vaccine were 64.2%, 57.7%, and 41.8%, respectively. In the multivariate analysis, factors affecting parents' acceptance of vaccines for their children were as follows: “Receiving antirheumatic medications regularly (AOR 5.40, 95% CI 1.10–26.33, p = 0.03), the previous history of getting special recommended vaccines (AOR 4.12, 95% CI 1.12–27.85, p = 0.03), relying on vaccines for ending pandemic (AOR 8.84, 95% CI 2.80–27.85, p = 0.001), complying with the pandemic measures entirely (AOR 5.24, 95% CI 1.46–18.74, p = 0.01)“. The two most common reasons for vaccine rejection were fear of the side effects of the vaccine and its possible interaction with rheumatic drugs used by children.ConclusionAccording to our survey, parents were more likely to accept a COVID-19 vaccine for themselves than their children. The success of COVID-19 vaccination programs sources highly on people's willingness to accept the vaccine. It is crucial to vaccinate children for achieving herd immunity and in terms of avoiding vaccine hesitancy. Larger data examining the causes of concerns in parents of both healthy children and children with chronic diseases should be delineated.     

Rapid Increase of Community SARS-CoV-2 Seroprevalence during Second Wave of COVID-19, Yaoundé, Cameroon

We conducted 2 independent population-based SARS-CoV-2 serosurveys in Yaoundé, Cameroon, during January 27–February 6 and April 24–May 19, 2021. Overall age-standardized SARS-CoV-2 IgG seroprevalence increased from 18.6% in the first survey to 51.3% in the second (p<0.001). This finding illustrates high community transmission during the second wave of COVID-19.     

The impact of seasonal influenza vaccination uptake on COVID-19 vaccination attitudes in a rural area in Greece

IntroductionPromoting vaccination for coronavirus disease 2019 (COVID-19), especially for high-risk groups such as the elderly and persons with comorbidities, is important for reducing the incidence of severe disease and death.MethodsRetrospective cross-sectional study of factors associated with COVID-19 vaccination, including previous influenza vaccination, among all persons who received medical services in a rural area in Crete, Greece, between October 2020-May 2021.ResultsAmong 3129 participants, receipt of influenza vaccination in 2020–21 was strongly associated with COVID-19 vaccination, as was influenza vaccination in 2019–20, albeit to a lesser extent. In addition, persons older than 59 years (with exception of those 90 + years old) and those who lived closer to the hospital/health center, were more likely to vaccinate for COVID-19. Persons younger than 40 years of age, females, persons with mental illness or neurologic disease, were also less likely to vaccinate for COVID-19 (all p < 0.001).ConclusionsCOVID-19 vaccination was more likely among those who were vaccinated for influenza before and during the pandemic. Access to healthcare services and specific comorbidities, were important influencers for vaccination, underlying the importance of tailored interventions to enforce vaccination in high-risk groups.     

Immediate adverse reactions following COVID-19 vaccination among 16–65-year-old Danish citizens

IntroductionThere is sparse knowledge of immediate adverse reactions following COVID-19 vaccination.ObjectiveThis study aimed to estimate the frequency and number of immediate adverse reactions following COVID-19 vaccination in a Danish population.MethodsThe study used data from the Danish population-based cohort study BiCoVac. The frequencies of 20 self-reported adverse reactions were estimated for each vaccine dose stratified by sex, age, and vaccine type. Also, the distributions of number of adverse reactions following each dose were estimated stratified by sex, age, vaccine type, and prior COVID-19 infection.ResultsA total of 889,503 citizens were invited and 171,008 (19 %) vaccinated individuals were included in the analysis. The most frequently reported adverse reaction following the first dose of COVID-19 vaccine was redness and/or pain at the injection site (20 %) while following the second and third dose, tiredness was the most frequently reported adverse reaction (22 % and 14 %, respectively). Individuals aged 26–35 years, females, and those with a prior COVID-19 infection were more likely to report adverse reactions compared with older individuals, males, and those with no prior COVID-19 infection, respectively. Following the first dose, individuals vaccinated with ChAdOx1-2 (AstraZeneca) reported more adverse reactions compared with individuals vaccinated with other vaccine types. Individuals vaccinated with mRNA-1273 (Moderna) reported more adverse reactions following the second and third dose compared with individuals vaccinated with BNT162b2 (Pfizer-BioNTech).ConclusionThe frequency of immediate adverse reactions was highest among females and younger persons, however, most of the Danish citizens did not experience immediate adverse reactions following COVID-19 vaccination.     

Factors Associated with Delayed or Missed Second-Dose mRNA COVID-19 Vaccination among Persons >12 Years of Age,United States

To identify demographic factors associated with delaying or not receiving a second dose of the 2-dose primary mRNA COVID-19 vaccine series, we matched 323 million single Pfizer-BioNTech (https://www.pfizer.com) and Moderna (https://www.modernatx.com) COVID-19 vaccine administration records from 2021 and determined whether second doses were delayed or missed. We used 2 sets of logistic regression models to examine associated factors. Overall, 87.3% of recipients received a timely second dose (≤42 days between first and second dose), 3.4% received a delayed second dose (>42 days between first and second dose), and 9.4% missed the second dose. Persons more likely to have delayed or missed the second dose belonged to several racial/ethnic minority groups, were 18–39 years of age, lived in more socially vulnerable areas, and lived in regions other than the northeastern United States. Logistic regression models identified specific subgroups for providing outreach and encouragement to receive subsequent doses on time.     

Age-Stratified Seroprevalence of SARS-CoV-2 Antibodies before and during the Vaccination Era,Japan, February 2020–March 2022

Japan has reported a relatively small number of COVID-19 cases. Because not all infected persons receive diagnostic tests for COVID-19, the reported number must be lower than the actual number of infections. We assessed SARS-CoV-2 seroprevalence by analyzing >60,000 samples collected in Japan (Tokyo Metropolitan Area and Hokkaido Prefecture) during February 2020–March 2022. The results showed that ≈3.8% of the population had become seropositive by January 2021. The seroprevalence increased with the administration of vaccinations; however, among the elderly, seroprevalence was not as high as the vaccination rate. Among children, who were not eligible for vaccination, infection was spread during the epidemic waves caused by the SARS-CoV-2 Delta and Omicron variants. Nevertheless, seroprevalence for unvaccinated children <5 years of age was as low as 10% as of March 2022. Our study underscores the low incidence of SARS-CoV-2 infection in Japan and the effects of vaccination on immunity at the population level.     

Parental health beliefs,intention, and strategies about covid-19 vaccine for their children: A cross-sectional analysis from five Arab countries in the Middle East

BackgroundThe issue around vaccination of children has brought divergent opinions among the populations across the globe and among the Arab population. There has been a low response rate to the calls for vaccination of children and this is reflective of the sentiments which parents may have towards their children being vaccinated. This study aims to explore the parents’ health beliefs, intentions, and strategies towards the COVID-19 vaccine for their children among Arab population.MethodsA cross-sectional study using an online survey from October to December 2021, was carried out in five Arab countries in the Middle East. A reliable health belief model (HBM) including five domains: severity, susceptibility, benefits, barriers and cues to action, was adopted. Chi-square, Mann–Whitney test, and multivariable logistic regression were performed for data analysis.ResultsThe survey response rate was 58 % (1154/2000). Only 56 % of Arab parents are intended to vaccinate their children against COVID-19. The mean scores of parental health belief are largely driven by their concern over the vaccine’s side effect (p = 0.001) followed by its efficacy, safety (p < 0.001), and scheduling difficulty (p = 0.029). However, strategies that were statistically encouraged parents to vaccinate their children included doctor’s recommendation, adequate information being provided, and acceptance of the vaccine by public (p < 0.001). Parents with one child were almost three times most likely to vaccinate their children (OR = 2.660, 95 %CI = 1.572–4.504, p < 0.001). Parents' desire to vaccinate their children is also influenced by other factors such as job loss owing to COVID-19 and the presence of a health worker in the family.ConclusionIntention of Arab parents to vaccinate their children via COVID-19 vaccine is still limited. Thus, it is essential for health care authorities to avail the information which will debunk the erroneous beliefs which some parents have developed towards the vaccination of children against COVID-19.     

The Effectiveness of Pfizer-BioNTech and Oxford-AstraZeneca Vaccines to Prevent Severe COVID-19 in Costa Rica: Nationwide,Ecological Study of Hospitalization Prevalence

BackgroundThe Costa Rican COVID-19 vaccination program has used Pfizer-BioNTech and Oxford-AstraZeneca vaccines. Real-world estimates of the effectiveness of these vaccines to prevent hospitalizations range from 90%-98% for two doses and from 70%-91% for a single dose. Almost all of these estimates predate the Delta variant.ObjectiveThe aim of this study is to estimate the dose-dependent effectiveness of COVID-19 vaccines to prevent severe illness in real-world conditions in Costa Rica, after the Delta variant became dominant.MethodsThis observational study is a secondary analysis of hospitalization prevalence. The sample is all 3.67 million adult residents living in Costa Rica by mid-2021. The study is based on public aggregated data of 5978 COVID-19–related hospital records from September 14, 2021, to October 20, 2021, and 6.1 million vaccination doses administered to determine hospitalization prevalence by dose-specific vaccination status. The intervention retrospectively evaluated is vaccination with Pfizer-BioNTech (78%) and Oxford-AstraZeneca (22%). The main outcome studied is being hospitalized.ResultsVaccine effectiveness against hospitalization (VEH) was estimated as 93.4% (95% CI 93.0-93.9) for complete vaccination and 76.7% (95% CI 75.0-78.3) for single-dose vaccination among adults of all ages. VEH was lower and more uncertain among older adults aged ≥58 years: 92% (95% CI 91%-93%) for those who had received full vaccination and 64% (95% CI 58%-69%) for those who had received partial vaccination. Single-dose VEH declined over time during the study period, especially in the older age group. Estimates were sensitive to possible errors in the population count used to determine the residual number of unvaccinated people when vaccine coverage is high.ConclusionsThe Costa Rican COVID-19 vaccination program that administered Pfizer-BioNTech and Oxford-AstraZeneca vaccines seems to be highly effective at preventing COVID-19–related hospitalization after the Delta variant became dominant. Even a single dose seems to provide some degree of protection, which is good news for people whose second dose of the Pfizer-BioNTech vaccine was postponed several weeks to more rapidly increase the number of people vaccinated with a first dose. Timely monitoring of vaccine effectiveness is important to detect eventual failures and motivate the public to get vaccinated by providing information regarding the effectiveness of the vaccines.     

Effectiveness of 3 COVID-19 Vaccines in Preventing SARS-CoV-2 Infections,January–May 2021, Aragon,Spain

Reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission is a worldwide challenge; widespread vaccination could be one strategy for control. We conducted a prospective, population-based cohort study of 964,258 residents of Aragon, Spain, during December 2020–May 2021. We used the Cox proportional-hazards model with vaccination status as the exposure condition to estimate the effectiveness of 3 coronavirus disease vaccines in preventing SARS-CoV-2 infection. Pfizer-BioNTech had 20.8% (95% CI 11.6%–29.0%) vaccine effectiveness (VE) against infection after 1 dose and 70.0% (95% CI 65.3%–74.1%) after 2 doses, Moderna had 52.8% (95% CI 30.7%–67.8%) VE after 1 dose and 70.3% (95% CI 52.2%–81.5%) after 2 doses, and Oxford-AstraZeneca had 40.3% (95% CI 31.8%–47.7%) VE after 1 dose. All estimates were lower than those from previous studies. Results imply that, although high vaccination coverage remains critical to protect people from disease, it will be difficult to effectively minimize transmission opportunities.     

Short-term safety of COVID-19 mRNA vaccines with respect to all-cause mortality in the older population in Norway

BackgroundThere have been concerns about COVID-19 vaccination safety among frail older individuals. We investigated the relationship between COVID-19 mRNA vaccination and mortality among individuals aged ≥ 70 years and whether mortality varies across four groups of health services used.MethodsIn this nationwide cohort study, we included 688,152 individuals aged ≥ 70 years at the start of the Norwegian vaccination campaign (December 27, 2020). We collected individual-level data from the Norwegian Emergency Preparedness Register for COVID-19. Vaccinated and unvaccinated individuals were matched (1:1 ratio) on the date of vaccination based on sociodemographic and clinical characteristics. The main outcome was all-cause mortality during 21 days after first dose of COVID-19 mRNA vaccination. Kaplan-Meier survival functions were estimated for the vaccinated and unvaccinated groups. We used Cox proportional-hazards regression to estimate hazard ratios (HRs) of death between vaccinated and unvaccinated individuals, with associated 95% confidence intervals (CIs), overall and by use of health services (none, home-based, short- and long-term nursing homes) and age group.ResultsBetween December 27, 2020, and March 31, 2021, 420,771 older individuals (61.1%) were vaccinated against COVID-19. The Kaplan-Meier estimates based on the matched study sample showed a small absolute risk difference in all-cause mortality between vaccinated and unvaccinated individuals, with a lower mortality in the vaccinated group (overall HR 0.28 [95% CI: 0.24–0.31]). Similar results were obtained in analyses stratified by use of health services and age group.ConclusionWe found no evidence of increased short-term mortality among vaccinated individuals in the older population after matching on sociodemographic and clinical characteristics affecting vaccination and mortality.