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. 2022 Jul 30;10(8):1223. doi: 10.3390/vaccines10081223

Table 3.

Summary of studies evaluating immunogenicity and efficacy/effectiveness of the second booster of COVID-19 vaccine.

Reference Design Findings
[67] Prospective, open-label, non-randomized study
Participants–healthcare workers ≥ 18Arms
treatment arm

  • 3 doses BNT162b2 + 4th dose of BNT162b2 (n = 154)

  • or mRNA-1273 (n = 120)age-matched control arm

  • 3 doses BNT162b2 (n = 547)

 Immunogenicity and efficacy

  • 9–10-fold increase in IgG RBD and neutralizing antibody titers 2 weeks after the 4th dose of both formulations.

  • 8–10-fold increase in live neutralization against Omicron and other variants with titer restoration to the peak after the 3rd dose of BNT162b2.

  • Efficacy against any SARS-CoV-2 infection: 30% for BNT162b2, 11% for mRNA-1273 compared to controls.

  • Percentage of Omicron infection: 18.3% for BNT162b2, 20.7% for mRNA-1273 and 25% in control arm.

  • Protection against symptomatic disease: 43% for BNT162b2, 31% for mRNA-1273 compared to controls.
[68] Retrospective real-world population-based study
Participants ≥ 60 yrs

  • four-dose group (8–14 days after 4th dose of BNT162b2)

  • internal control four-dose group (3–5 days after 4th dose of BNT162b2)

  • control three-dose group (persons after 3 doses of BNT162b2, eligible for 4th dose, but not yet vaccinated)

 Effectiveness

  • The adjusted rate of severe COVID-19 in the fourth week after receipt of the 4th dose was lower than that in the three-dose group by a factor of 3.5 (95% confidence interval [CI], 2.7 to 4.6) and lower than that in the internal control group by a factor of 2.3 (95% CI, 1.7 to 3.3).

  • Protection against severe disease did not wane during the 6 weeks after receipt of the 4th dose.

  • The adjusted rate of confirmed infection in the fourth week after receipt of the 4th dose was lower than that in the three-dose group by a factor of 2.0 (95% CI, 1.9 to 2.1) and lower than that in the internal control group by a factor of 1.8 (95% CI, 1.7 to 1.9); this protection waned in later weeks.
[70] Retrospective real-world population-based study
Participants ≥ 60 yrs

  • four-dose group (after 4th dose of BNT162b2)

  • Control three-dose group (persons after 3 doses of BNT162b2, eligible for 4th dose, but not yet vaccinated)

 Effectiveness–protection assessed 7–30 days and 14–30 days after 4th dose against

  • SARS-CoV-2 infection confirmed by RT-PCR–45% and 52%

  • Symptomatic COVID-19–55% and 61%

  • COVID-19-related hospitalization–68% and 72%

  • Severe COVID-19–62% and 64%

  • COVID-19-related death–74% and 76%