Estimation of Real-World Vaccination Effectiveness of mRNA COVID-19 Vaccines against Delta and Omicron Variants in Japan

Abstract

A resurgence of COVID-19-positive cases has been observed in many countries in the latter half of 2021. The primary reasons for this resurgence are the waning immunity of vaccination after the second dose of vaccination and the changes in public behavior due to temporal convergence. The vaccination effectiveness for the omicron and delta variants has been reported from some countries, but it is still unclear for several other regions worldwide. Here, we numerically derived the effectiveness of vaccination for infection protection in individuals and populations against viral variants for the entire Japanese population (126 million). The waning immunity of vaccination for the delta variant of Japanese individuals was 93.8% (95% CI: 93.1–94.6%) among individuals <65 years of age and 95.0% (95% CI: 95.6–96.9%) among individuals ≥65 years of age. We found that waning immunity of vaccination in individuals >65 years of age was lower than in those <65 years of age, which may be attributable to human behavior and a higher vaccination rate among individuals >65 years of age. From the reported data of 25,187 positive cases with confirmed omicron variant in Tokyo in January 2022, the effectiveness of vaccination was also estimated at 62.1% (95% CI: 48–66%) compared to that of the delta variant. Derived effectiveness of vaccination would be useful to discuss the vaccination strategy for the booster shot, as well as the status of herd immunity.

The Vaccine Efficacy Against the SARS-CoV-2 Omicron: A Systemic Review and Meta-Analysis

“…The included studies had a total sample of around one hundred million (N = 148260342) participants and of these, 74.2% were fully vaccinated ( n = 110076947) with at least two-doses of COVID-19 vaccines ( Table 1 ). Among the 13 studies, 1 study reported the effectiveness of the BNT162b2 (Pfizer–BioNTech), ChAdOx1 (AstraZeneca), mRNA-1273 (Moderna) and JNJ-78436735 vaccines ( 25 ); 1 study reported the effectiveness of the BNT162b2 and ChAdOx1 vaccines ( 24 ); 3 studies reported the effectiveness of the BNT162b2, ChAdOx1, and mRNA-1273 vaccines ( 12 , 21 , 22 ); 5 studies reported the effectiveness of the BNT162b2, and mRNA-1273 vaccines ( 14 , 16 , 17 , 20 , 23 ); 2 studies reported the effectiveness of the BNT162b2 vaccine ( 18 , 19 ), and 1 study reported the effectiveness of the mRNA-1273 vaccine ( 15 ).…”

Did the Tokyo Olympic Games enhance the transmission of COVID-19? An interpretation with machine learning

“…Note that the vaccination rate of BNT162b2 in Japan is approximately 90%. Furthermore, based on the waning immunity for infection protection, s was defined as 0.24 to match the model [ 29 , 30 ].…”

OMICRON: Virology, immunopathogenesis, and laboratory diagnosis

“…39 In 20% of individuals, T cell reactivity to the Omicron spike is lowered by more than 50%. 40 The majority of Omicron epitopes are sequence conserved and preserve affinity to HLA-I. 41 In some cases, the immune response against SARS-CoV-2 may be dysregulated, leading to a severe hyperinflammatory condition, CRS.…”

“…Shortly after the booster immunization, T cell responsiveness to Omicron is improved 39 . In 20% of individuals, T cell reactivity to the Omicron spike is lowered by more than 50% 40 . The majority of Omicron epitopes are sequence conserved and preserve affinity to HLA‐I 41 …”