Question explored with the scientific record
what is the estimated efficacy of this season's covid vaccine
The short version: no retrieved study measures this season's vaccine against this season's virus, so any specific efficacy number would be invented.
The records here are all from 2021 to 2024, and none test the 2025-2026 formulation. What they show is a moving target. Against the original strain, two mRNA doses ran about 94-95% effective at preventing symptomatic illness [3][5][7]. Against Delta, that fell to roughly 40-90% depending on the study and outcome [1][2][5]. Against Omicron, two doses dropped to about 34-37%, and a booster lifted it back to 60-72% [1]. By 2024, ACIP was already tracking safety signals, not just efficacy, including Guillain-Barré and ischemic stroke in older adults after mRNA shots [10].
The pattern is clear: every new variant has eroded protection against infection, while protection against severe disease and death has held up better [1][4][6]. Antibody levels also wane sharply, dropping about 84% by six months after the second dose [8]. That is why boosters keep being recommended [9].
What is missing matters as much as what is here. No retrieved study compares vaccinated against genuinely unvaccinated people for this season's shot. No long-term safety data exists for repeated boosting. The evidence base is a series of snapshots of older formulations, not a verdict on the one being offered now.
My call: the evidence cannot support a specific efficacy figure for this season's vaccine. Confidence: not clear.
Sources used 10
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SARS‐CoV‐2 Omicron variant: Immune escape and vaccine development
This narrative review synthesizes evidence that the SARS-CoV-2 Omicron variant carries numerous spike mutations, shows increased transmissibility and substantial evasion of neutralizing antibodies from vaccines and prior infection, and considers vaccine booster and variant-speci…
DOI: 10.1002/mco2.126 -
Prediction of long-term kinetics of vaccine-elicited neutralizing antibody and time-varying vaccine-specific efficacy against the SARS-CoV-2 Delta variant by clinical endpoint
A modeling study predicting long-term kinetics of vaccine-elicited SARS-CoV-2 neutralizing antibodies and time-varying, vaccine-specific protection against the Delta variant across four vaccine platforms, incorporating booster (third-dose) effects and age groups.
DOI: 10.1186/s12916-022-02249-9 -
Comparisons Of Mrna Vaccine from Different Manufactures
A comparative review of three mRNA COVID-19 vaccines (Pfizer-BioNTech BNT162b2, Moderna mRNA-1273, and Walvax/ARCoV) covering target proteins, efficacy against infection and severe disease, safety, and cost, with recommendations tailored to cohorts and affordability.
DOI: 10.54097/hset.v45i.7392 -
The Effectiveness Of COVID-19 Vaccination in Protecting Older Adults Against Emerging Infectious and Virulent Strains
A systematic review of 10 studies found COVID-19 vaccination protects older adults against severe disease and mortality, booster doses sustain protection, and mRNA vaccines appear more effective than inactivated vaccines.
DOI: 10.54097/9qxcpk04 -
The Systematic Research of The Comparison of Moderna Covid-19 Vaccine and Pfizer Covid-19 Vaccine
A narrative review comparing Moderna and Pfizer/BioNTech COVID-19 vaccines, outlining their mechanisms, clinical efficacy including against the Delta variant, safety profiles, storage considerations, and future directions.
DOI: 10.54097/hset.v45i.7384 -
A systematic review of effectiveness of BNT162b2 mRNA and ChAdOx1 adenoviral vector COVID-19 vaccines in the general population
A systematic review of 11 observational studies found that BNT162b2 mRNA and ChAdOx1 adenoviral vector COVID-19 vaccines provide equivalent and generally high real-world effectiveness against SARS-CoV-2 infection and COVID-19-related morbidity and mortality, increasing over time…
DOI: 10.1186/s42269-021-00607-w -
Mecanismo y diseño de vacunas para el sars-cov-2, revisión narrativa
This narrative review describes SARS-CoV-2 vaccine mechanisms and designs, reporting that mRNA vaccines (BNT162b2 and mRNA-1273) demonstrate the highest efficacy (93-95%), adenovirus vector vaccines show 66.9-91.6% efficacy, and inactivated CoronaVac shows 83.5%, with rare safet…
DOI: 10.18566/medupb.v43n1.a10 -
Overview of Anti-SARS-CoV-2 Immune Response Six Months after BNT162b2 mRNA Vaccine
In 178 never-infected healthcare workers, BNT162b2 vaccination induced declining anti-Spike IgG and neutralizing titers over six months, while T-cell responses remained variable; switched memory B cells increased and Th17 cells correlated with neutralizing antibodies.
DOI: 10.3390/vaccines10020171 -
The effectiveness of the first dose COVID-19 booster vs. full vaccination to prevent SARS-CoV-2 infection and severe COVID-19 clinical event: a meta-analysis and systematic review of longitudinal studies
A first COVID-19 booster dose, compared with full two-dose vaccination, reduced the risk of SARS-CoV-2 infection, ICU admission, and death and elicited stronger humoral and cellular immune responses, per a meta-analysis of 10 studies.
DOI: 10.3389/fpubh.2023.1165611 -
June 2024 ACIP Meeting Update: Influenza, COVID-19, RSV, and Other Vaccines
ACIP's June 2024 meeting update outlines updated US pediatric vaccine recommendations for 2024–2025 across influenza, COVID-19, RSV, and other vaccines, summarizing safety surveillance, emerging vaccine options, and policy changes to broaden access.
DOI: 10.1542/peds.2024-068310