Project description:ObjectiveTo compare the effectiveness of a primary covid-19 vaccine series plus booster doses with a primary series alone for the prevention of hospital admission with omicron related covid-19 in the United States.DesignMulticenter observational case-control study with a test negative design.SettingHospitals in 18 US states.Participants4760 adults admitted to one of 21 hospitals with acute respiratory symptoms between 26 December 2021 and 30 June 2022, a period when the omicron variant was dominant. Participants included 2385 (50.1%) patients with laboratory confirmed covid-19 (cases) and 2375 (49.9%) patients who tested negative for SARS-CoV-2 (controls).Main outcome measuresThe main outcome was vaccine effectiveness against hospital admission with covid-19 for a primary series plus booster doses and a primary series alone by comparing the odds of being vaccinated with each of these regimens versus being unvaccinated among cases versus controls. Vaccine effectiveness analyses were stratified by immunosuppression status (immunocompetent, immunocompromised). The primary analysis evaluated all covid-19 vaccine types combined, and secondary analyses evaluated specific vaccine products.ResultsOverall, median age of participants was 64 years (interquartile range 52-75 years), 994 (20.8%) were immunocompromised, 85 (1.8%) were vaccinated with a primary series plus two boosters, 1367 (28.7%) with a primary series plus one booster, and 1875 (39.3%) with a primary series alone, and 1433 (30.1%) were unvaccinated. Among immunocompetent participants, vaccine effectiveness for prevention of hospital admission with omicron related covid-19 for a primary series plus two boosters was 63% (95% confidence interval 37% to 78%), a primary series plus one booster was 65% (58% to 71%), and for a primary series alone was 37% (25% to 47%) (P<0.001 for the pooled boosted regimens compared with a primary series alone). Vaccine effectiveness was higher for a boosted regimen than for a primary series alone for both mRNA vaccines (BNT162b2 (Pfizer-BioNTech): 73% (44% to 87%) for primary series plus two boosters, 64% (55% to 72%) for primary series plus one booster, and 36% (21% to 48%) for primary series alone (P<0.001); mRNA-1273 (Moderna): 68% (17% to 88%) for primary series plus two boosters, 65% (55% to 73%) for primary series plus one booster, and 41% (25% to 54%) for primary series alone (P=0.001)). Among immunocompromised patients, vaccine effectiveness for a primary series plus one booster was 69% (31% to 86%) and for a primary series alone was 49% (30% to 63%) (P=0.04).ConclusionDuring the first six months of 2022 in the US, booster doses of a covid-19 vaccine provided additional benefit beyond a primary vaccine series alone for preventing hospital admissions with omicron related covid-19.Readers' noteThis article is a living test negative design study that will be updated to reflect emerging evidence. Updates may occur for up to two years from the date of original publication.
Project description:We estimated the effectiveness of booster doses of monovalent mRNA COVID-19 vaccines against Omicron-associated severe outcomes among adults in Ontario, Canada. We used a test-negative design to estimate vaccine effectiveness (VE) against hospitalization or death among SARS-CoV-2-tested adults aged ≥50 years from January 2 to October 1, 2022, stratified by age and time since vaccination. We also compared VE during BA.1/BA.2 and BA.4/BA.5 sublineage predominance. We included 11,160 cases and 62,880 tests for test-negative controls. Depending on the age group, compared to unvaccinated adults, VE was 91-98% 7-59 days after a third dose, waned to 76-87% after ≥240 days, was restored to 92-97% 7-59 days after a fourth dose, and waned to 86-89% after ≥120 days. VE was lower and declined faster during BA.4/BA.5 versus BA.1/BA.2 predominance, particularly after ≥120 days. Here we show that booster doses of monovalent mRNA COVID-19 vaccines restored strong protection against severe outcomes for at least 3 months after vaccination. Across the entire study period, protection declined slightly over time, but waned more during BA.4/BA.5 predominance.
Project description:Abstract Background US recommendations for COVID‐19 vaccine boosters have expanded in terms of age groups covered and numbers of doses recommended, whereas evolution of Omicron sublineages raises questions about ongoing vaccine effectiveness. Methods We estimated effectiveness of monovalent COVID‐19 mRNA booster vaccination versus two‐dose primary series during a period of Omicron variant virus circulation in a community cohort with active illness surveillance. Hazard ratios comparing SARS‐CoV‐2 infection between booster versus primary series vaccinated individuals were estimated using Cox proportional hazards models with time‐varying booster status. Models were adjusted for age and prior SARS‐CoV‐2 infection. The effectiveness of a second booster among adults ≥50 years of age was similarly estimated. Results The analysis included 883 participants ranging in age, from 5 to >90 years. Relative effectiveness was 51% (95% CI: 34%, 64%) favoring the booster compared with primary series vaccination and did not vary by prior infection status. Relative effectiveness was 74% (95% CI: 57%, 84%) at 15 to 90 days after booster receipt, but declined to 42% (95% CI: 16%, 61%) after 91 to 180 days, and to 36% (95% CI: 3%, 58%) after 180 days. The relative effectiveness of a second booster compared to a single booster was 24% (95% CI: −40% to 61%). Conclusions An mRNA vaccine booster dose added significant protection against SARS‐CoV‐2 infection, but protection decreased over time. A second booster did not add significant protection for adults ≥50 years of age. Uptake of recommended bivalent boosters should be encouraged to increase protection against Omicron BA.4/BA.5 sublineages.
Project description:ObjectivesTo evaluate the cost-effectiveness of a booster strategy in the United States.MethodsWe developed a decision-analytic Markov model of COVID-19 to evaluate the cost-effectiveness of a booster strategy of the Pfizer-BioNTech BNT162b2 (administered 6 months after the second dose) among older adults from a healthcare system perspective.ResultsCompared with 2 doses of BNT162b2 without a booster, the booster strategy in a 100,000 cohort of older adults would incur an additional cost of $3.4 million in vaccination cost but save $6.7 million in direct medical cost and gain 3.7 quality-adjusted life-years in 180 days. This corresponds to a benefit-cost ratio of 1.95 and a net monetary benefit of $3.4 million. Probabilistic sensitivity analysis indicates that a booster strategy has a high chance (67%) of being cost-effective. Notably, the cost-effectiveness of the booster strategy is highly sensitive to the population incidence of COVID-19, with a cost-effectiveness threshold of 8.1/100,000 person-day. If vaccine efficacies reduce by 10%, 30%, and 50%, this threshold will increase to 9.7/100,000, 13.9/100,000, and 21.9/100,000 person-day, respectively.ConclusionOffering the BNT162b2 booster to older adults aged ≥65 years in the United States is likely to be cost-effective. Less efficacious vaccines and boosters may still be cost-effective in settings of high SARS-CoV-2 transmission.
Project description:We estimated the effectiveness of booster doses of monovalent and bivalent mRNA COVID-19 vaccines against Omicron-associated severe outcomes among adults aged ≥50 years in Ontario, Canada. Monovalent and bivalent mRNA COVID-19 booster doses provided similar strong initial protection against severe outcomes. Uncertainty remains around waning of protection from these vaccines.
Project description:ImportanceCOVID-19 vaccine boosters or third doses are recommended for adolescents and adults who completed their initial COVID-19 vaccine course more than 5 months prior. Minimal data are available on COVID-19 vaccine booster or third dose reactogenicity among pregnant and lactating individuals.ObjectiveTo describe the reactions to the booster or third dose of the COVID-19 vaccine and vaccine experiences among pregnant and lactating individuals.Design, setting, and participantsBeginning in October 2021, a follow-up Research Electronic Data Capture (REDCap) survey regarding a COVID-19 vaccine booster or third dose was sent to 17 504 participants in an ongoing online prospective cohort study on COVID-19 vaccines among pregnant and lactating individuals. A convenience sample of adults enrolled in the online prospective study who were pregnant, lactating, or neither pregnant nor lactating at the time of their booster or third dose was eligible for this follow-up survey; 17 014 (97.2%) completed the follow-up survey.ExposureReceipt of a booster or third dose of the COVID-19 vaccine.Main outcomes and measuresSelf-reported vaccine reactions less than 24 hours after the dose.ResultsAs of April 4, 2022, 17 014 eligible participants (mean [SD] age, 33.3 [3.5] years) responded to the booster or third dose survey; of these, 2009 (11.8%) were pregnant at the time of their booster or third dose, 10 279 (60.4%) were lactating, and 4726 (27.8%) were neither pregnant nor lactating. After a COVID-19 booster or third dose, most individuals (14 074 of 17 005 [82.8%]) reported a local reaction, and 11 542 of 17 005 (67.9%) reported at least 1 systemic symptom. Compared with individuals who were neither pregnant nor lactating, pregnant participants were more likely to report any local reaction to a COVID-19 booster or third dose (adjusted odds ratio [aOR], 1.2; 95% CI, 1.0-1.4; P = .01) but less likely to report any systemic reaction (aOR, 0.7; 95% CI, 0.6-0.8; P < .001). Most pregnant (1961 of 2009 [97.6%]) and lactating (9866 of 10 277 [96.0%]) individuals reported no obstetric or lactation concerns after vaccination.Conclusions and relevanceThis study suggests that COVID-19 vaccine boosters or third doses were well tolerated among pregnant and lactating individuals. Data to evaluate tolerability of boosters or additional doses among pregnant and lactating individuals will be important as they are considered for these populations.
Project description:Vaccine reluctance among healthcare workers (HCW) can have widespread negative ramifications, including modeling behavior for the general population and challenges with maintaining a healthy workforce so we can respond to a resurgence of the pandemic. We previously reported that only one-third of HCW were willing to take the vaccine as soon as it became available prior to its Emergency Use Authorization (EUA). Here, we re-examine the attitude toward COVID-19 vaccines among HCW several months after the vaccines have been made widely available. In this study, only 7.9% (n = 107) of respondents were hesitant to take the first or second dose of the vaccine. Younger age (18-40 years) and lower level of education attainment (GED or less) were associated with higher vaccine hesitancy, whereas self-identified Asian racial identity was associated with greater acceptance of COVID-19 vaccination. Among the vaccine-hesitant group, more respondents noted mistrust of regulatory authorities (45.3%), government (48.6%), and pharmaceutical companies (50%) than mistrust of doctors (25.4%). Nearly two-thirds of respondents were concerned that vaccination may be ineffective against new strains and booster doses may be required; however, vaccine-hesitant respondents' acceptance of a hypothetical booster dose was only 14.3%. Overall, vaccine hesitancy was observed to have demographic predictors similar to those previously reported; the hesitancy of some US HCW to receive booster doses may reflect a general hesitancy to receive other forms of vaccination.
Project description:The surge in coronavirus disease 2019 (COVID-19) caused by the Omicron variants of the severe acute respiratory syndrome coronavirus 2 necessitates researches to inform vaccine effectiveness (VE) and other preventive measures to halt the pandemic. A test-negative case-control study was conducted among adults (age ≥18 years) who were at-risk for COVID-19 and presented for nasopharyngeal real-time polymerase chain reaction testing during the Omicron variant-dominant period in Thailand (1 January 2022-15 June 2022). All participants were prospectively followed up for COVID-19 development for 14 days after the enrolment. Vaccine effectiveness was estimated and adjusted for characteristics associated with COVID-19. Of the 7971 included individuals, there were 3104 cases and 4867 controls. The adjusted VE among persons receiving 2-dose, 3-dose, and 4-dose vaccine regimens for preventing infection and preventing moderate-to-critical diseases were 33%, 48%, 62% and 60%, 74%, 76%, respectively. The VE were generally higher among those receiving the last dose of vaccine within 90 days compared to those receiving the last dose more than 90 days prior to the enrolment. The highest VE were observed in individuals receiving the 4-dose regimen, CoronaVac-CoronaVac-ChAdOx1 nCoV-19-BNT162b2 for both preventing infection (65%) and preventing moderate-to-critical diseases (82%). Our study demonstrated increased VE along with an increase in number of vaccine doses received. Current vaccination programmes should focus on reducing COVID-19 severity and mandate at least one booster dose. The heterologous boosters with viral vector and mRNA vaccines were highly effective and can be used in individuals who previously received the primary series of inactivated vaccine.
Project description:BackgroundCOVID-19 is a viral disease caused by the SARS-CoV-2, leading to several variants. This study aimed to examine the effectiveness of booster doses against the Delta and Omicron variants over different follow-up times. Study Design: This was a longitudinal meta-analysis.MethodsSearches were performed in PubMed, Cochrane Library, Scopus, and Web of Science databases, and eighty studies were selected for investigation. The analyses were separately performed on the unvaccinated control group (UNVCG) and the complete two doses of the vaccine control group (C2DCG) against Delta and Omicron variants. Three outcomes were examined, including symptomatic infection, hospitalization, and death.ResultsVaccine effectiveness (VE) in UNVCG studies for symptomatic infection revealed a non-linear trend against Omicron with a peak of 67.3%, declining to 27.1% after 25 weeks after a booster dose. The mean of VE for hospitalization over time started to decrease after four weeks against Omicron and after eight weeks against Delta. The VE reached a peak at week eight (96.0%) and started to decline with a VE of 93.3% after 20 weeks after the booster dose against Delta. It was 90.8% at week four and decreased to 73.4% after 25 weeks after the booster dose against Omicron. VE in the C2DCG studies demonstrated more decreases in outcomes over time.ConclusionOur findings showed a tendency to decrease effectiveness over time based on outcomes and variants. The early protection levels were lower in Omicron. Moreover, the VE decrease over time was stronger in Omicron compared to the Delta variant.
Project description:The bivalent (original and Omicron BA.4/BA.5) mRNA-1273 COVID-19 vaccine was authorized to offer broader protection against COVID-19. We conducted a matched cohort study to evaluate the effectiveness of the bivalent vaccine in preventing hospitalization for COVID-19 (primary outcome) and medically attended SARS-CoV-2 infection and hospital death (secondary outcomes). Compared to individuals who did not receive bivalent mRNA vaccination but received ≥2 doses of any monovalent mRNA vaccine, the relative vaccine effectiveness (rVE) against hospitalization for COVID-19 was 70.3% (95% confidence interval, 64.0%-75.4%). rVE was consistent across subgroups and not modified by time since last monovalent dose or number of monovalent doses received. Protection was durable ≥3 months after the bivalent booster. rVE against SARS-CoV-2 infection requiring emergency department/urgent care and against COVID-19 hospital death was 55.0% (50.8%-58.8%) and 82.7% (63.7%-91.7%), respectively. The mRNA-1273 bivalent booster provides additional protection against hospitalization for COVID-19, medically attended SARS-CoV-2 infection, and COVID-19 hospital death.