Vaccine booster inoculation against Omicron strains exerts a certain protective effect even 4 months after inoculation

The mRNA vaccine against the new coronavirus that has been prevalent since 2020 is basically 'completed' by inoculating twice, but it is known that the protective power decreases as time passes after inoculation, 3 The second inoculation (booster inoculation) is advocated. However, little is known about how long booster vaccination will last for 'Delta' and 'Omicron' strains, so the Centers for Disease Control and Prevention (CDC) in the United States gathered data and gathered data. We have clarified the protective effect 2 months and 4 months after the booster inoculation.

Waning 2-Dose and 3-Dose Effectiveness of mRNA Vaccines Against COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Adults During Periods of Delta and Omicron Variant Predominance — VISION Network, 10 States, August 2021–January 2022 | MMWR

Booster protection from omicron hospital stay dips from 91% to 78% | Ars Technica
https://arstechnica.com/science/2022/02/cdc-boosters-mostly-holding-against-omicron-but-4th-shots-may-still-be-ahead/

The CDC collected data on emergency and emergency care (ED / UC) patients in more than 10 states and inpatients to evaluate the vaccine efficacy (VE) of booster inoculation.

The results showed that VE was lower when the Omicron strain was dominant than when the Delta strain was dominant.

In the case of ED / UC patients, 87% of VEs during the period when the Omicron strain was dominant were 87% 2 months after inoculation and 66% 4 months after inoculation. For inpatients, 91% were 2 months after vaccination and 78% were 4 months after vaccination. The fact that the VE of inpatients was higher than that of ED / UC patients tended to be seen in both the Delta strain dominant period and the Omicron strain dominant period.

The vaccine efficacy was 37% more than 5 months after the second vaccination.

The CDC concluded that vaccination should always be kept up-to-date to prevent outpatients and hospitalizations infected with the new coronavirus, that is, 'booster vaccination should be done' four months later. It is also said that it is a result of strengthening the importance of considering further additional doses for protection against outpatients and hospitalizations related to the new corona and improvement of the situation due to the degree of decrease in the efficacy of the vaccine.