Thursday, December 01, 2022

Study finds efficacy of modern COVID vaccine reaches 94% after 120 days

Recently posted a research paper jama network open Assessed the durability of immunity conferred by the coronavirus disease 2019 (COVID-19) messenger ribonucleic acid (mRNA)-1273 vaccine.

Study: Durability Of Protection Against Symptomatic Covid-19 Among Participants Of The Mrna-1273 Sars-Cov-2 Vaccine Trial.  Image Credit: Redo/ShutterstockStudy: Durability of protection against symptomatic COVID-19 among participants of the mRNA-1273 SARS-CoV-2 vaccine trial. Image credit: redo/shutterstock


Assessing the longevity of immunity provided by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccines is one of the public health priorities. In addition, the findings are needed to inform guidelines on non-pharmaceutical interventions and booster vaccination for COVID-19.

about the study

In the current work, researchers evaluated the mRNA-1273 P301 Cohort Study, an ongoing phase 3 randomized, placebo-controlled trial of 30 415 US adults, to assess the efficacy and safety of mRNA-1273 SARS-CoV-2. ) Vaccination.

The team used a per-protocol population for this cohort analysis, which included 28,451 subjects who were SARS-CoV-2-negative at the start of the study and received two vaccine doses until the completion of the blind phase. Volunteers received the initial vaccine dose between 27 July and 23 October 2020.

At least two systemic symptoms or one respiratory symptom or sign defined COVID-19 cases and were validated by a SARS-CoV-2-positive reverse transcriptase-polymerase chain reaction (RT-PCR) test result. Before enrollment, all participants presented a written informed consent. The scientists followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting standards.

The authors used a Cox regression model representing the log hazard ratio for vaccine effect as a piecewise-linear function of time since vaccination, at timestamps 120, 80, and 40 days after dose 1 With the change points where the log hazard occurs, the slope of the ratio was estimated to change to obtain an accurate estimate of the safety. Using this formulation the entire curve of vaccine effectiveness (VE) at the current probability of disease can be estimated.

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The investigators used calendar time after the start of the study as the time scale for assessment rather than time since subject randomization because the frequency of COVID-19 community transmission varies over time. was dramatically different. This enabled them to compare the incidence of disease between unvaccinated and vaccinated people on the same calendar date. The study was performed with version 4.1 R package DOVE, with the dove2 function.

Study findings

Study results indicated that the placebo group had 14,164 participants with 769 SARS-CoV-2 infection cases, while the mRNA-1273 group included 14,287 subjects with 56 COVID-19 events. VE consistently peaked at 94.1% at day 120, which steadily increased to 92.6% at day 40 after the initial dose. At about 120 days, VE began to decline, falling to 89.6% by 200 days.

Efficacy Of Mrna-1273 Sars-Cov-2 Vaccine In Reducing The Current Risk Of Symptomatic Covid-19

Efficacy of mRNA-1273 SARS-CoV-2 vaccine in reducing the current risk of symptomatic COVID-19

These findings suggest that VE was decreasing over time and was more insightful about the length of protection against symptomatic disease than prior estimates. Although there was substantial ambiguity in predicting VE near the completion of blind follow-up, the degree of safety was high even after 200 days of dosing 1.

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According to the study data, 94.1% were evaluated in interim screening against COVID-19 Modern VE symptomatic SARS-CoV-2 infection and 93.2% at the end of the blind phase. Comparing these two estimates, it appeared that VE was decreasing slightly.

Nevertheless, since VE estimation was achieved under the assumption that VE was stable during the analysis period, it represents an average of time-varying vaccine effects over a broad research period, when the incidence rather than post-investigation VE. So the weighted is the period. Therefore, this comparison was insufficient to identify the true extent of the deficiency.

The team said phase III trials provide placebo-regulated efficacy estimates for less than seven months after dose 1 because of the overlap of placebo participants with the vaccine group. Indeed, in the present investigation, some cases of COVID-19 occurred after six months, making it impossible to determine the extent of VE decline after blind follow-up. The authors note that observational studies may reveal information about the long-term benefits of vaccines.

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