The impact of COVID-19 vaccines on the Case Fatality Rate: The importance of monitoring breakthrough infections

Inferring the true number of SARS-CoV-2 infections in Japan

“…Age-specific estimates of IFR were obtained from Ref. [ 19 ], which were calculated prior to vaccination, pharmaceutical measures, and evolution of less severe variants; however, recognizing these dynamics have a pronounced effect in reducing the IFR [ 20 , 21 ], we adjusted the estimates accordingly. Specifically, we linearly decreased the estimated IFR of each age to a maximum of 55% starting from February 17, 2021 (corresponding to the first vaccination in Japan) to the end of study period [ 22 ].…”

COVID-19 transmission dynamics and the impact of vaccination: modelling, analysis and simulations

“…This implies that if there were no vaccination, then the peak infections would have occurred on Effect of vaccination efficacy, 1. Recently, di Lego et al [48] argued that unless vaccinated people are also tested for COVID-19 infection, it is difficult to unravel the effect of vaccines in reducing case fatality rate (CFR). Therefore, the effect of varying vaccine efficacy rate 1 on the dynamics of the disease among the infectious population was investigated for the second, third and fourth waves.…”

“…The results in figure 8c,d show that a higher vaccination rate reduces the disease incidence although by smaller margins in the fourth wave. Moreover, for most countries, studies have shown that despite a high proportion of vaccinated individuals, the CFR does not significantly decrease for almost a year after vaccine uptake [48][49][50][51].…”

Exploring immune evasion of SARS-CoV-2 variants using a pseudotyped system

“…These variants have developed a greater ability to evade the immune system [ 7 ]. The Omicron variant, with its significant immune evasion capability, has been associated with an increase in breakthrough infections [ 8 ]. Since late 2022, the Omicron subvariant XBB.1.5 has become the dominant lineage of SARS-CoV-2.…”