Monovalent COVID-19 vaccines targeting the XBB.1.5 Omicron variant were introduced in September 2023. In the absence of randomized controlled trials demonstrating their efficacy, information on real-world vaccine effectiveness (VE) is needed.
Objective:
To determine XBB.1.5 COVID-19 VE and the extent to which it declines over time.
Design:
Target trial emulation.
Setting:
U.S. Veterans Health Administration.
Participants:
Eligible XBB.1.5 vaccine recipients were matched 1:1 to unvaccinated persons in 7 sequential biweekly trials with enrollment from 2 October 2023 through 3 January 2024.
Intervention:
XBB.1.5 COVID-19 vaccination versus no XBB.1.5 vaccination.
Measurements:
Outcomes were ascertained through 10 May 2024 and included any positive result on a SARS-CoV-2 test from day 10 after the matched index date, subsequent hospitalization within 1 day before or 10 days after the positive result, or death within 30 days after the positive result. Vaccine effectiveness was estimated as 100 × (1 − risk ratio).
Results:
Participants (91.3% male; mean age, 69.9 years) included 587 137 pairs of vaccinated and matched unvaccinated persons. Over a mean follow-up of 176 days (range, 118 to 211 days), VE was −3.26% (95% CI, −6.78% to −0.22%) against documented SARS-CoV-2 infection, 16.64% (CI, 6.47% to 25.77%) against SARS-CoV-2–associated hospitalization, and 26.61% (CI, 5.53% to 42.32%) against SARS-CoV-2–associated death. When estimated at 60, 90, and 120 days, respectively, VE against documented infection (14.21%, 7.29%, and 3.15%), hospitalization (37.57%, 30.84%, and 25.25%), or death (54.24%, 44.33%, and 30.25%) showed substantial waning.
Conclusion:
COVID-19 vaccines targeting the XBB.1.5 variant of Omicron were not effective in preventing infection and had relatively low VE against hospitalization and death, which declined rapidly over time.
Vaccine effectiveness (VE) against documented SARS-CoV-2 infection was -3.26% (95% CI, -6.78% to -0.22%), indicating a statistically significant higher infection rate in vaccinated individuals compared to the unvaccinated control group.
The small reported benefit against COVID-19-associated hospitalization and death is likely due to healthy vaccinee bias, as those who get vaccinated tend to have lower baseline risks.
These findings corroborate FIVE other studies demonstrating negative efficacy:
Nakatani et al – Vaccinated individuals had an 85% increased odds of COVID-19 infection compared to unvaccinated individuals (Adjusted OR = 1.85 – 95% CI: 1.33–2.57).
Eythorsson et al – Among individuals vaccinated, the odds of reinfection are 42% higher for those who received 2 or more doses compared to those with 1 dose or less (95% CI: 1.13–1.78).
Chemaitelly et al – The effectiveness of Pfizer-BioNTech (BNT162b2) against symptomatic BA.1 and BA.2 Omicron infections dropped from 46.6% and 51.7% (1–3 months post-dose) to -17.8% and -12.1% (≥7 months). Similarly, Moderna (mRNA-1273) declined from 71.0% and 35.9% to -10.2% and -20.4% over the same period.
Shrestha et al (Cleveland Clinic) – The risk of COVID-19 increased with the number of vaccine doses received. Individuals with one prior dose had a 107% higher risk of COVID-19 (HR = 2.07, 95% CI: 1.70–2.52) compared to those with no prior doses. Those with more than three doses faced a 253% higher risk (HR = 3.53, 95% CI: 2.97–4.20).
Feldstein et al (CDC) – Children vaccinated with Pfizer-BioNTech without prior SARS-CoV-2 infection were 159% more likely to get infected (HR = 2.59, 95% CI: 1.27–5.28) and 257% more likely to develop symptomatic COVID-19 (HR = 3.57, 95% CI: 1.10–11.63) compared to unvaccinated children without prior infection.
The Negative Efficacy of COVID-19 mRNA Injections Has Been Demonstrated
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