Determining the duration of protection provided by coronavirus vaccines is particularly important in determining the vaccination schedule and making public health decisions.
The Doctors of the Therapeutic Clinic of the Medical School of the National and Kapodistrian University of Athens Theodora Psaltopoulou, Giannis Danasis, Panos Malandrakis and Thanos Dimopoulos (Rector of EKPA) summarize the latest data from the relevant publication of an article in the Lancet by DR Feikin et al. : https: //doi.org/10.1016/S0140-6736 (22) 00152-0).
The researchers conducted a systematic review and meta-analysis of all relevant articles in the literature from June 17, 2021 to December 2, 2021.
The studies included were randomized clinical trials and observational studies. A total of data from 18 studies, which were performed before the predominance of the Omicron strain, were included.
Based on the critical evaluation of the studies, the probability of error (bias) was judged low for the 3 studies, moderate for the 8 studies and severe for the 7 studies. 78 COVID-19 vaccine efficacy evaluations were performed, namely 38 for Cominarty vaccine (Pfizer / BioNTech), 23 for mRNA-1273 (Moderna), 9 for Ad26.COV2.S (Johnson) and 8 for Vaxzevria (AstraZeneca) .
After how long does the effectiveness of the vaccine decrease?
Overall, the efficacy of full vaccination against SARS-CoV-2 infection decreased at 21 months post-vaccination by 21% compared with efficacy at 1 month post-vaccination regardless of age.
In older vaccinated persons (over 50 years) efficacy over the same period decreased by 21%.
In addition, the efficacy of full vaccination against symptomatic COVID-19 disease was reduced at 25 months post-vaccination by 25% compared with efficacy at 1 month post-vaccination regardless of age. In older vaccinated persons (over 50 years of age) the efficacy against symptomatic COVID-19 was reduced by 32% over the same period.
In addition, the efficacy of full vaccination against severe COVID-19 disease decreased at 6 months post-vaccination by 10% compared with efficacy at 1 month post-vaccination regardless of age.
In older vaccinated (over 50 years) the efficacy against severe COVID-19 disease during the same period was also reduced by 10%. Overall, the efficacy of the vaccine against severe disease remained at levels above 70% over time up to 6 months after vaccination. Decreased efficacy of vaccines against SARS-CoV-2 infection can be attributed to the decline of immunity to the virus over time, as well as to the emergence and prevalence of new strains of the virus.
