Social determinants of adult COVID-19 vaccine acceptance and uptake in a Brazilian urban informal community: a longitudinal time-to-event study (preprint)

Residents of informal urban settlements have a high risk of COVID-19 exposure and have less access to medical care, making vaccine-driven prevention critical in this vulnerable population. Despite robust vaccination campaigns in Brazil, vaccine uptake and timing continue to be influenced by social factors and contribute to health disparities. To address this, we conducted a sequential survey in a cohort of 717 adults in an urban favela in Salvador, Brazil where participants were interviewed in 2020, before vaccines were rolled out, and in 2022, after primary and booster dose distribution. We collected data on demographics, social characteristics, and COVID-19 vaccination status and intent. Primary series uptake was high (91.10% for 1st dose and 94.74% for 2nd dose among eligible); however, booster uptake was lower (63.51% of eligible population) at the time of the second interview, suggesting a decreasing interest in vaccination. To account for both vaccine refusal and delays, we conducted a Cox time-to-event analysis of dose uptake using sequential independent outcomes. Exposure times were determined by dose eligibility date to account for age and comorbidities. Intent to vaccinate in 2020 (hazard ratio [HR]: 1.54, CI: [1.05, 1.98]) and age (HR: 1.27, CI: [1.01, 2.08]) were associated with higher vaccination rates for the 1st dose. Males were less likely to receive the 1st dose (HR: 0.61, CI: [0.35, 0.83]), and, compared to catholics, 2nd dose uptake was lower for those identifying with Pentecostalism (HR: 0.49, CI: [0.37, 0.66]) and without a religion (HR: 0.49, CI: [0.37, 0.66]), with the latter association disappearing after controlling by age. Risk perception was associated with 2nd dose uptake (HR: 1.15, CI: [1.08, 1.26]). The role of sex and religion in vaccination behavior highlights the need for targeted outreach and interfacing with local organizations. The data offers lessons to build a long-term COVID-19 vaccination strategy beyond availability.

Covid-19 vaccine acceptance among individuals incarcerated in Connecticut state jails.

BACKGROUND: Vaccine hesitancy is common among incarcerated populations and, despite vaccination programs, vaccine acceptance within residents remains low, especially within jails. With the goal of assessing the Connecticut DOC's COVID-19 vaccine program within jails we examined if residents of DOC operated jails were more likely to become vaccinated following incarceration than in the community. Specifically, we conducted a retrospective cohort analysis among people who spent at least one night in a DOC-operated jail between February 2 and November 8, 2021, and were eligible for vaccination at the time of incarceration (intake). We compared the vaccination rates before and after incarceration using an age-adjusted survival analysis with a time-varying exposure of incarceration and an outcome of vaccination. RESULTS: During the study period, 3,716 people spent at least one night in jail and were eligible for vaccination at intake. Of these residents, 136 were vaccinated prior to incarceration, 2,265 had a recorded vaccine offer, and 479 were vaccinated while incarcerated. The age-adjusted hazard of vaccination following incarceration was significantly higher than prior to incarceration (12.5; 95% Confidence Intervals: 10.2-15.3). CONCLUSIONS: We found that residents were more likely to become vaccinated in jail than in the community. Though these findings highlight the utility of vaccination programs within jails, the low level of vaccination in this population speaks to the need for additional program development within jails and the community.

Evidence of Leaky Protection Following COVID-19 Vaccination and SARS-CoV-2 Infection in a US Correctional Facility Population (preprint)

Whether SARS-CoV-2 infection and COVID-19 vaccines confer exposure-dependent ("leaky") protection remains unknown. We examined the effect of prior infection and vaccination on infection risk among residents of Connecticut correctional facilities during periods of predominant Omicron and Delta transmission. Residents with cell, unit, and no documented exposures to SARS-CoV-2 infected residents were matched by facility and date. During the Omicron period, prior infection and vaccination reduced the infection risk of residents without a documented exposure (Hazards ratio: infection, 0.36 [0.25-0.54]; vaccination, 0.57 [0.42-0.78]) and with cellblock exposures (infection, 0.61 [0.49-0.75]; vaccination, 0.69 [0.58-0.83]) but not with cell exposures (infection, 0.89 [0.58-1.35]; vaccination, 0.96 [0.64-1.46]). Associations were similar during the Delta period and when analyses were restricted to residents who underwent testing. These findings suggest that SARS-CoV-2 infection and COVID-19 vaccination may be leaky, highlighting the potential benefits of pairing vaccination with non-pharmaceutical interventions in densely crowded settings.

Covid-19 Vaccine Acceptance Among People Incarcerated in Connecticut State Jails (preprint)

Objective: To assess the Connecticut Department of Corrections (DOC) COVID-19 vaccine program within jails. Methods: We conducted a retrospective cohort analysis among people who were incarcerated in a DOC-operated jail between February 2 and November 8, 2021, and were eligible for vaccination at the time of incarceration (intake). We compared the vaccination rates before and after incarceration using an age-adjusted survival analysis with a time-varying exposure of incarceration and an outcome of vaccination. Results: During the study period, 3,716 people spent at least 1 night in jail and were eligible for vaccination at intake. Of these residents, 136 were vaccinated prior to incarceration, 2,265 had a recorded vaccine offer, and 476 were vaccinated while incarcerated. The age-adjusted hazard of vaccination following incarceration was significantly higher than prior to incarceration (12.5; 95% CI: 10.2-15.3). Conclusions: We found that residents were more likely to become vaccinated in jail than the community. Though these findings highlight the utility of vaccination programs within jails, the low level of vaccination in this population speaks to the need for additional program development within jails and the community.

Effectiveness of CoronaVac, ChAdOx1, BNT162b2 and Ad26.COV2.S among individuals with prior SARS-CoV-2 infection in Brazil (preprint)

Background. COVID-19 vaccines have proven highly effective among SARS-CoV-2 naive individuals, but their effectiveness in preventing symptomatic infection and severe outcomes among individuals with prior infection is less clear. Methods. Utilizing national COVID-19 notification, hospitalization, and vaccination datasets from Brazil, we performed a case-control study using a test-negative design to assess the effectiveness of four vaccines (CoronaVac, ChAdOx1, Ad26.COV2.S and BNT162b2) among individuals with laboratory-confirmed prior SARS-CoV-2 infection. We matched RT-PCR positive, symptomatic COVID-19 cases with RT-PCR-negative controls presenting with symptomatic illnesses, restricting both groups to tests performed at least 90 days after an initial infection. We used multivariable conditional logistic regression to compare the odds of test positivity, and the odds of hospitalization or death due to COVID-19, according to vaccination status and time since first or second dose of vaccines. Findings. Among individuals with prior SARS-CoV-2 infection, vaccine effectiveness against symptomatic infection [≥] 14 days from vaccine series completion was 39.4% (95% CI 36.1-42.6) for CoronaVac, 56.0% (95% CI 51.4-60.2) for ChAdOx1, 44.0% (95% CI 31.5-54.2) for Ad26.COV2.S, and 64.8% (95% CI 54.9-72.4) for BNT162b2. For the two-dose vaccine series (CoronaVac, ChAdOx1, and BNT162b2), effectiveness against symptomatic infection was significantly greater after the second dose compared with the first dose. Effectiveness against hospitalization or death [≥] 14 days from vaccine series completion was 81.3% (95% CI 75.3-85.8) for CoronaVac, 89.9% (95% CI 83.5-93.8) for ChAdOx1, 57.7% (95% CI -2.6-82.5) for Ad26.COV2.S, and 89.7% (95% CI 54.3-97.7) for BNT162b2.

Change in COVID-19 risk over time following vaccination with CoronaVac: A test-negative case-control study (preprint)

Objective To estimate the change in odds of covid-19 over time following primary series completion of the inactivated whole virus vaccine, CoronaVac (Sinovac Biotech) in Sao Paulo State, Brazil. Design Test negative case-control study. Setting Community testing for covid-19 in Sao Paulo state, Brazil. Participants Adults aged 18-120 years who were residents of Sao Paulo state, without a previous laboratory-confirmed covid-19 infection, who received two doses of CoronaVac, and underwent reverse transcription polymerase chain reaction (RT-PCR) testing for SARS-CoV-2 from 17 January to 30 September 2021. Main outcome measures RT-PCR-confirmed symptomatic covid-19 and associated hospital admissions and deaths. Cases were pair-matched to test-negative controls by age (in 5-year bands), municipality of residence, healthcare worker (HCW) status, and date of RT-PCR test ({+/-}3 days). Conditional logistic regression was adjusted for sex, number of covid-19-associated comorbidities, race, and previous acute respiratory infection. Results From 137,820 eligible individuals, 37,929 cases with symptomatic covid-19 and 25,756 test-negative controls with covid-19 symptoms were formed into 37,929 matched pairs. Adjusted odds ratios of symptomatic covid-19 increased with time since series completion, and this increase was greater in younger individuals, and among HCWs compared to non-HCWs. Adjusted odds ratios of covid-19 hospitalisation or death were significantly increased from 98 days since series completion, compared to individuals vaccinated 14-41 days previously: 1.40 (95% confidence interval 1.09 to 1.79) from 98-125 days, 1.55 (1.16 to 2.07) from 126-153 days, 1.56 (1.12 to 2.18) from 154-181 days, and 2.12 (1.39-3.22) from 182 days. Conclusions In the general population of Sao Paulo state, Brazil, an increase in odds of moderate and severe covid-19 outcomes was observed over time following primary series completion with CoronaVac.

Effectiveness of the ChAdOx1 vaccine in the elderly during SARS-CoV-2 Gamma variant transmission in Brazil (preprint)

BackgroundA two-dose regimen of ChAdOx1 coronavirus disease 19 (Covid-19) vaccine with an inter-dose interval of three months has been implemented in many countries with restricted vaccine supply. However, there is limited evidence for the effectiveness of ChAdOx1 by dose in elderly populations in countries with high prevalence of the Gamma variant of severe acute respiratory syndrome 2 (SARS-CoV-2). MethodsWe conducted a test-negative case-control study to estimate the effectiveness of ChAdOx1 vaccine in adults aged 60 years or older during a Gamma-variant-associated epidemic in Sao Paulo state, Brazil, between 17 January and 2 July 2021. Cases and matched test-negative controls were individuals, identified from surveillance databases, who experienced an acute respiratory illness and underwent SARS-CoV-2 RT-PCR testing. We used conditional logistic regression to estimate the effectiveness by dose against RT-PCR-confirmed Covid-19, Covid-19 hospitalization, and Covid-19-related death. Results61,164 individuals were selected into matched case-control pairs. Starting [≥]28 days after the first dose, adjusted effectiveness of a single dose of ChAdOx1 was 33.4% (95% CI, 26.4 to 39.7) against Covid-19, 55.1% (95% CI, 46.6 to 62.2) against hospitalization, and 61.8% (95% CI, 48.9 to 71.4) against death. Starting [≥]14 days after the second dose, the adjusted effectiveness of the two-dose schedule was 77.9% (95% CI, 69.2 to 84.2) against Covid-19, 87.6% (95% CI, 78.2 to 92.9) against hospitalization, and 93.6% (95% CI, 81.9 to 97.7) against death. ConclusionsCompletion of the ChAdOx1 vaccine schedule afforded significantly increased protection over a single dose against mild and severe Covid-19 outcomes in elderly individuals during widespread Gamma variant transmission.

Effectiveness of the CoronaVac vaccine in the elderly population during a P.1 variant-associated epidemic of COVID-19 in Brazil: A test-negative case-control study (preprint)

ObjectiveTo estimate the effectiveness of the inactivated whole-virus vaccine, CoronaVac, against symptomatic COVID-19 in the elderly population of Sao Paulo State, Brazil during widespread circulation of the Gamma variant. DesignTest negative case-control study. SettingHealth-care facilities in Sao Paulo State, Brazil. Participants43,774 adults aged 70 years or older who were residents of Sao Paulo State and underwent SARS-CoV-2 RT-PCR testing from January 17 to April 29, 2021. 26,433 cases with symptomatic COVID-19 and 17,622 symptomatic, test negative controls were selected into 7,950 matched pairs, according to age, sex, self-reported race, municipality of residence, prior COVID-19 status and date of RT-PCR testing. InterventionVaccination with a two-dose regimen of CoronaVac. Main outcome measuresRT-PCR confirmed symptomatic COVID-19 and COVID-19 associated hospitalizations and deaths. ResultsAdjusted vaccine effectiveness against symptomatic COVID-19 was 18.2% (95% CI, 0.0 to 33.2) in the period 0-13 days after the second dose and 41.6% (95% CI, 26.9 to 53.3) in the period [≥]14 days after the second dose. Adjusted vaccine effectiveness against hospitalisations was 59.0% (95% CI, 44.2 to 69.8) and against deaths was 71.4% (95% CI, 53.7 to 82.3) in the period [≥]14 days after the second dose. Vaccine effectiveness [≥]14 days after the second dose declined with increasing age for the three outcomes, and among individuals aged 70-74 years it was 61.8% (95% CI, 34.8 to 77.7) against symptomatic disease, 80.1% (95% CI, 55.7 to 91.0) against hospitalisations and 86.0% (95% CI, 50.4 to 96.1) against deaths. ConclusionsVaccination with CoronaVac was associated with a reduction in symptomatic COVID-19, hospitalisations and deaths in adults aged 70 years or older in a setting with extensive Gamma variant transmission. However, significant protection was not observed until completion of the two-dose regimen, and vaccine effectiveness declined with increasing age amongst this elderly population. Summary boxesO_ST_ABSWhat is already known on this topicC_ST_ABSRandomised controlled trials (RCT) have yielded varying estimates (51 to 84%) for the effectiveness of the inactivated whole-virus vaccine, CoronaVac, against symptomatic COVID-19. Current evidence is limited on whether CoronaVac is effective against severe disease or death caused by the SARS-CoV-2 variant of concern, Gamma, or in the setting of extensive Gamma variant circulation. More evidence is needed for the real-world effectiveness of CoronaVac and other inactivated vaccines among elderly individuals, a population that was underrepresented in RCTs of these vaccines. What this study addsA two-dose regimen of CoronaVac provides significant protection against symptomatic COVID-19, hospitalisations and deaths among adults [≥]70 years of age in the setting of widespread Gamma variant transmission. Significant protection did not occur until [≥]14 days after administration of the second dose of CoronaVac. The effectiveness of CoronaVac declines with increasing age in the elderly population.