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ABSTRACTEmerging SARS-CoV-2 sublineages continue to cause serious COVID-19 disease, but most individuals have not received any COVID-19 vaccine for >1 year. Assessment of long-term effectiveness of bivalent COVID-19 vaccines against circulating sublineages is important to inform the potential need for vaccination with updated vaccines. In this test-negative study at Kaiser Permanente Southern California, sequencing-confirmed BA.4/BA.5- or XBB-related SARS-CoV-2-positive cases (September 1, 2022 to June 30, 2023), were matched 1:3 to SARS-CoV-2-negative controls. We assessed mRNA-1273 bivalent relative (rVE) and absolute vaccine effectiveness (VE) compared to ≥2 or 0 doses of original monovalent vaccine, respectively. The rVE analysis included 20,966 cases and 62,898 controls. rVE (95%CI) against BA.4/BA.5 at 14–60 days and 121–180 days was 52.7% (46.9–57.8%) and 35.5% (−2.8–59.5%) for infection, and 59.3% (49.7–67.0%) and 33.2% (−28.2–68.0%) for Emergency Department/Urgent Care (ED/UC) encounters. For BA.4/BA.5-related hospitalizations, rVE was 71.3% (44.9–85.1%) and 52.0% (−1.2–77.3%) at 14–60 days and 61–120 days, respectively. rVE against XBB at 14–60 days and 121–180 days was 48.8% (33.4–60.7%) and −3.9% (−18.1–11.3%) for infection, 70.7% (52.4–82.0%) and 15.7% (−6.0–33.2%) for ED/UC encounters, and 87.9% (43.8–97.4%) and 57.1% (17.0–77.8%) for hospitalization. VE and subgroup analyses (age, immunocompromised status, previous SARS-CoV-2 infection) results were similar to rVE analyses. rVE of mRNA-1273 bivalent vaccine against BA.4/BA.5 and XBB infections, ED/UC encounters, and hospitalizations waned over time. Periodic revaccination with vaccines targeting emerging variants may be important in reducing COVID-19 morbidity and mortality.

Abstract 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.

In this study, the authors estimate the effectiveness of the mRNA-1273 (Moderna) vaccine for Omicron subvariants using data from the USA on ~31,000 cases and ~92,000 matched controls. They find that effectiveness against infection waned rapidly after third and fourth doses, but effectiveness against hospitalization remained high.

Summary: Background: Phase 3 trials found mRNA-1273 was highly effective in preventing COVID-19. We conducted a prospective cohort study at Kaiser Permanente Southern California (KPSC) to determine the real-world vaccine effectiveness (VE) of mRNA-1273 in preventing COVID-19 infection and severe disease. Methods: For this planned interim analysis, individuals aged ≥18 years receiving 2 doses of mRNA-1273 ≥24 days apart (18/12/2020-31/03/2021) were 1:1 matched to randomly selected unvaccinated individuals by age, sex, and race/ethnicity, with follow-up through 30/06/2021. Outcomes were COVID-19 infection (SARS-CoV-2 positive molecular test or COVID-19 diagnosis code) or severe disease (COVID-19 hospitalization and COVID-19 hospital death). Adjusted hazard ratios (aHR) and confidence intervals (CI) for COVID-19 outcomes comparing vaccinated and unvaccinated individuals were estimated by Cox proportional hazards models accounting for multiple comparisons. Adjusted VE was calculated as (1-aHR)x100. Whole genome sequencing was performed on SARS-CoV-2 positive specimens from the KPSC population. Findings: This analysis included 352,878 recipients of 2 doses of mRNA-1273 matched to 352,878 unvaccinated individuals. VE (99·3% CI) against COVID-19 infection was 87·4% (84·8–89·6%). VE against COVID-19 hospitalization and hospital death was 95·8% (90·7–98·1%) and 97·9% (66·9-99·9%), respectively. VE was higher against symptomatic (88·3% [98·3% CI: 86·1–90·2%]) than asymptomatic COVID-19 (72·7% [53·4–84·0%]), but was generally similar across age, sex, and racial/ethnic subgroups. VE among individuals with history of COVID-19 ranged from 8·2–33·6%. The most prevalent variants were Alpha (41·6%), Epsilon (17·5%), Delta (11·5%), and Gamma (9·1%), with Delta increasing to 54·0% of variants by June 2021. Interpretation: These interim results provide reassuring evidence of the VE of 2 doses of mRNA-1273 across age, sex, and racial/ethnic subgroups, and against asymptomatic and symptomatic COVID-19, and severe COVID-19 outcomes. Among individuals with history of COVID-19, mRNA-1273 vaccination may offer added protection beyond immunity acquired from prior infection. Longer follow-up is needed to fully evaluate VE of mRNA-1273 against emerging SARS-CoV-2 variants. Funding: Moderna Inc.

BackgroundWe conducted a prospective cohort study at Kaiser Permanente Southern California to study the vaccine effectiveness (VE) of mRNA-1273 over time and during the emergence of the Delta variant.MethodsThe cohort for this planned interim analysis consisted of individuals aged ≥18 years receiving 2 doses of mRNA-1273 through June 2021, matched 1:1 to randomly selected unvaccinated individuals by age, sex, and race/ethnicity, with follow-up through September 2021. Outcomes were SARS-CoV-2 infection, and COVID-19 hospitalization and hospital death. Cox proportional hazards models were used to estimate adjusted hazard ratios (aHR) with 95% confidence intervals (CIs) comparing outcomes in the vaccinated and unvaccinated groups. Adjusted VE (%) was calculated as (1-aHR)x100. HRs and VEs were also estimated for SARS-CoV-2 infection by age, sex, race/ethnicity, and during the Delta period (June-September 2021). VE against SARS-CoV-2 infection and COVID-19 hospitalization was estimated at 0-Results927,004 recipients of 2 doses of mRNA-1273 were matched to 927,004 unvaccinated individuals. VE (95% CI) was 82.8% (82.2-83.3%) against SARS-CoV-2 infection, 96.1% (95.5-96.6%) against COVID-19 hospitalization, and 97.2% (94.8-98.4%) against COVID-19 hospital death. VE against SARS-CoV-2 infection was similar by age, sex, and race/ethnicity, and was 86.5% (84.8-88.0%) during the Delta period. VE against SARS-CoV-2 infection decreased from 88.0% at 0-ConclusionsThese interim results provide continued evidence for protection of 2 doses of mRNA-1273 against SARS-CoV-2 infection over 8 months post-vaccination and during the Delta period, and against COVID-19 hospitalization and hospital death.