Effectiveness of third vaccine dose for coronavirus disease 2019 during the Omicron variant pandemic: a prospective observational study in Japan

Abstract

The administration of a third booster dose of messenger ribonucleic acid (mRNA) vaccines against coronavirus disease 2019 (COVID-19) has progressed worldwide. Since January 2022, Japan has faced a nationwide outbreak caused by the Omicron variant, which occurred simultaneously with the progression of mass vaccination with the third booster dose. Therefore, this study evaluated the effectiveness of the third dose of vaccine by reverse transcription-polymerase chain reaction (RT-PCR) test using nasopharyngeal swab samples from adults aged ≥ 18 years tested after having close contact with COVID-19 cases between January and May 2022. Participants who completed only one dose were excluded from the study. Among the 928 enrolled participants, 139 had never been vaccinated, 609 had completed two doses, 180 had completed three doses before the swab test, and the overall RT-PCR test positivity rate in each group was 48.9%, 46.0%, and 32.2%, respectively. The vaccine effectiveness of the third dose to prevent infection after close contact was approximately 40% (95% confidence interval: 20–60%), which was the highest at 10–70 days after receiving the third dose. In conclusion, the effectiveness of the three-dose mRNA COVID-19 vaccine after close contact during the Omicron outbreak is approximately 40%.

Timing of BNT162b2 vaccine prior to COVID‐19 infection, influence disease severity in patients with hematologic malignancies: Results from a cohort study

“…Several studies conducted during the Omicron surge in the general population, demonstrated the benefit of a booster dose (third or fourth) when administered in close proximity to the infection but effectiveness loss with time. [35][36][37][38] In an analysis of immunocompromised patients during the Omicron predominance, vaccine effectiveness against COVID-19-related hospitalization was highest between 7 and 89 days after the booster dose, 39 which is in accordance with our results. Studies in patients with lymphoproliferative disease did not find a correlation between vaccine status and COVID-19-related outcomes, although the timing of vaccination was not specified in these studies.…”

Antibody response to third and fourth BNT162b2 mRNA booster vaccinations in healthcare workers in Tokyo, Japan

“…Recent studies on the effectiveness of the third dose of the vaccine found improved efficacy against SARS-CoV-2 infection and a reduction in hospitalization [ [8] , [9] , [10] , [11] , [12] , [13] , [14] ]. However, most studies on the effect of the third vaccination have been limited to a relatively short period of time after the third dose, and few longitudinal analyses of the effects of the third vaccination with an anti–SARS-CoV-2 vaccine have been reported.…”

The Fourth Dose of mRNA COVID-19 Vaccine Following 12 Different Three-Dose Regimens: Safety and Immunogenicity to Omicron BA.4/BA.5

“…The third booster dose elicits a high immune response against infection [ 6 , 7 ]. A field study demonstrated that the third dose increased vaccine effectiveness against disease severity [ 8 , 9 ], and reduced hospitalization rates [ 7 , 10 ].…”