Effectiveness of two and three doses of COVID-19 mRNA vaccines against infection, symptoms, and severity in the pre-omicron era: A time-dependent gradient.

BACKGROUND: Vaccines were developed and deployed to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This study aimed to characterize patterns in the protection provided by the BNT162b2 and mRNA-1273 mRNA vaccines against a spectrum of SARS-CoV-2 infection symptoms and severities. METHODS: A national, matched, test-negative, case-control study was conducted in Qatar between January 1 and December 18, 2021, utilizing a sample of 238,896 PCR-positive tests and 6,533,739 PCR-negative tests. Vaccine effectiveness was estimated against asymptomatic, symptomatic, severe coronavirus disease 2019 (COVID-19), critical COVID-19, and fatal COVID-19 infections. Data sources included Qatar's national databases for COVID-19 laboratory testing, vaccination, hospitalization, and death. RESULTS: Effectiveness of two-dose BNT162b2 vaccination was 75.6% (95% CI: 73.6-77.5) against asymptomatic infection and 76.5% (95% CI: 75.1-77.9) against symptomatic infection. Effectiveness against each of severe, critical, and fatal COVID-19 infections surpassed 90%. Immediately after the second dose, all categories-namely, asymptomatic, symptomatic, severe, critical, and fatal COVID-19-exhibited similarly high effectiveness. However, from 181 to 270 days post-second dose, effectiveness against asymptomatic and symptomatic infections declined to below 40%, while effectiveness against each of severe, critical, and fatal COVID-19 infections remained consistently high. However, estimates against fatal COVID-19 often had wide 95% confidence intervals. Analogous patterns were observed in three-dose BNT162b2 vaccination and two- and three-dose mRNA-1273 vaccination. Sensitivity analyses confirmed the results. CONCLUSION: A gradient in vaccine effectiveness exists and is linked to the symptoms and severity of infection, providing higher protection against more symptomatic and severe cases. This gradient intensifies over time as vaccine immunity wanes after the last vaccine dose. These patterns appear consistent irrespective of the vaccine type or whether the vaccination involves the primary series or a booster.

Addressing bias in the definition of SARS-CoV-2 reinfection: implications for underestimation.

Introduction: Reinfections are increasingly becoming a feature in the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, accurately defining reinfection poses methodological challenges. Conventionally, reinfection is defined as a positive test occurring at least 90 days after a previous infection diagnosis. Yet, this extended time window may lead to an underestimation of reinfection occurrences. This study investigated the prospect of adopting an alternative, shorter time window for defining reinfection. Methods: A longitudinal study was conducted to assess the incidence of reinfections in the total population of Qatar, from February 28, 2020 to November 20, 2023. The assessment considered a range of time windows for defining reinfection, spanning from 1 day to 180 days. Subgroup analyses comparing first versus repeat reinfections and a sensitivity analysis, focusing exclusively on individuals who underwent frequent testing, were performed. Results: The relationship between the number of reinfections in the population and the duration of the time window used to define reinfection revealed two distinct dynamical domains. Within the initial 15 days post-infection diagnosis, almost all positive tests for SARS-CoV-2 were attributed to the original infection. However, surpassing the 30-day post-infection threshold, nearly all positive tests were attributed to reinfections. A 40-day time window emerged as a sufficiently conservative definition for reinfection. By setting the time window at 40 days, the estimated number of reinfections in the population increased from 84,565 to 88,384, compared to the 90-day time window. The maximum observed reinfections were 6 and 4 for the 40-day and 90-day time windows, respectively. The 40-day time window was appropriate for defining reinfection, irrespective of whether it was the first, second, third, or fourth occurrence. The sensitivity analysis, confined to high testers exclusively, replicated similar patterns and results. Discussion: A 40-day time window is optimal for defining reinfection, providing an informed alternative to the conventional 90-day time window. Reinfections are prevalent, with some individuals experiencing multiple instances since the onset of the pandemic.

Knowledge, attitude, and practices regarding human papilloma virus vaccination among physicians in Qatar.

BACKGROUND: The human papilloma virus is a global problem that affects sexually active women and men, with cervical cancer being the most serious associated disease. Most cervical cancer cases can be prevented by vaccination against the human papilloma virus early in life. The objective of this study was to assess the knowledge, attitudes, and practices among physicians working in Qatar, regarding the human papilloma virus, infection, and prevention using vaccines. STUDY-DESIGN: This was a cross-sectional study using quantitative data collection. METHODOLOGY: An online survey targeting physicians working in Qatar was conducted, using a web-based pretested questionnaire. The questionnaire comprised four sections capturing a few demographic details, 33 questions in the Knowledge Section, 12 questions eliciting the attitude, and 14 practice-related questions. Mean knowledge score was calculated and those with a score more than the mean score were considered to have sufficient knowledge. Association between knowledge and attitude/practices/independent variables were looked for using bivariate and multivariate analysis. Logistic regression was used to identify the predictors for recommending human papilloma virus vaccines. RESULTS: Of the 557 physicians who participated, 83.7% had sufficient knowledge, but only 69.1% knew that human papilloma virus vaccines were available in Qatar. The majority (89.4%) knew that human papilloma virus infection could be asymptomatic and 96.1% knew at least one symptom; 77% believed the human papilloma virus vaccine would substantially decrease the chances of human papilloma virus infection and related cancers and 46.5% felt physicians were less motivated to promote the human papilloma virus vaccine. The perceived barriers to community acceptance of the human papilloma virus vaccine were lack of awareness regarding the relationship between human papilloma virus and cervical cancer (61.6%), doubts regarding efficacy (32.5%), fear regarding safety (26.9%), concern that the human papilloma virus vaccination may encourage risky sexual behavior (26.8%), and perceived low-risk (23.3%) and cost (24.6%). Only 21.5% commonly discussed sexual health with their clients. More than one-third were not interested in recommending the human papilloma virus vaccine. Bivariate analysis showed nationality, specialization, discussing with patients, and recommending vaccine to be significantly associated with knowledge. Bivariate and regression analysis identified that female gender and physician's religion were significant predictors to recommend the human papilloma virus vaccine. CONCLUSION: Most physicians have good knowledge. Less than one-fourth commonly discussed sexual health with their clients. More than one-third were not interested in recommending the human papilloma virus vaccine. This issue might affect the human papilloma virus vaccination program implementation if not well addressed.

To achieve the 2030 goal, targeted education are required to address the gaps in the knowledge and attitudes of health care providers and tailored advocacy activities with suitable approaches to empower them in addressing the perceived barriers and misunderstanding and to encourage them in proactive enrollment through effective communication. Nearly half the physicians had sufficient knowledge regarding human papilloma virus infection and human papilloma virus vaccine; however, quite a high number did not know that the vaccines were available in Qatar. Physicians were not commonly discussing sexual health with their clients; however, a reasonable proportion recommended the human papilloma virus vaccine. The proportion of physicians willing to vaccinate their adolescent daughter with the human papilloma virus was not high. Many reasons were stated, of which not being sexually active was the most common. Physician-perceived barriers to community acceptance of human papilloma virus vaccines included gap in knowledge of the relationship between the human papilloma virus and cancer, concerns regarding vaccine efficacy and safety, and cost and fear of risky sexual behavior that could be encouraged by vaccination. These gaps and challenges mandate the setting of appropriate strategies and organizing interventions and services for the enhancement of a comprehensive cervical cancer control program in Qatar.