Duration of immune protection of SARS-CoV-2 natural infection against reinfection in Qatar

BACKGROUNDThe future of the SARS-CoV-2 pandemic hinges on virus evolution and duration of immune protection of natural infection against reinfection. We investigated duration of protection afforded by natural infection, the effect of viral immune evasion on duration of protection, and protection against severe reinfection, in Qatar, between February 28, 2020 and June 5, 2022. METHODSThree national, matched, retrospective cohort studies were conducted to compare incidence of SARS-CoV-2 infection and COVID-19 severity among unvaccinated persons with a documented SARS-CoV-2 primary infection, to incidence among those infection-naive and unvaccinated. Associations were estimated using Cox proportional-hazard regression models. RESULTSEffectiveness of pre-Omicron primary infection against pre-Omicron reinfection was 85.5% (95% CI: 84.8-86.2%). Effectiveness peaked at 90.5% (95% CI: 88.4-92.3%) in the 7th month after the primary infection, but waned to [~]70% by the 16th month. Extrapolating this waning trend using a Gompertz curve suggested an effectiveness of 50% in the 22nd month and <10% by the 32nd month. Effectiveness of pre-Omicron primary infection against Omicron reinfection was 38.1% (95% CI: 36.3-39.8%) and declined with time since primary infection. A Gompertz curve suggested an effectiveness of <10% by the 15th month. Effectiveness of primary infection against severe, critical, or fatal COVID-19 reinfection was 97.3% (95% CI: 94.9- 98.6%), irrespective of the variant of primary infection or reinfection, and with no evidence for waning. Similar results were found in sub-group analyses for those [≥]50 years of age. CONCLUSIONSProtection of natural infection against reinfection wanes and may diminish within a few years. Viral immune evasion accelerates this waning. Protection against severe reinfection remains very strong, with no evidence for waning, irrespective of variant, for over 14 months after primary infection.

Quantifying COVID-19 vaccination hesitancy during early vaccination rollout in Canada

BackgroundUnderstanding vaccination hesitancy during early vaccination rollout in Canada can help the governments vaccination efforts in education and outreach, which may help eventually achieving herd immunity. This study uses an online survey to assess vaccination hesitancy in population subgroups in Canada. MethodPanel members from the nationally representative Angus Reid Forum were randomly invited to complete an online survey on their experiencing with COVID-19 symptoms and testing, as well as intention to vaccination against COVID-19. Respondents were asked "when a vaccine against the coronavirus becomes available to you, will you get vaccinated or not?" Vaccination hesitancy was defined as choosing "No - I will not get a coronavirus vaccination" as a response. Results14,621 panel members (46% male and 53% female) completed the survey. Although the respondents overrepresent age 60+ and higher levels of education, other demographics, the prevalences of smoking, obesity, diabetes and hypertension were comparable to the Canadian national census and health surveys. COVID-19 vaccination hesitancy is relatively low overall (9%). Being a resident of Alberta (predicted probability = 15%), aged 40-59 (OR = 0.87, 0.78 - 0.97, predicted probability = 12%), identifying as a visible minority (OR = 0.56, 0.37 - 0.84, predicted probability = 15%), having some college level education or lower (predicted probability = 14%), or living in households of at least 5 are related to greater vaccination hesitancy (OR = 0.82, 0.76 - 0.88, predicted probability = 13%). ConclusionOur study enhances the understanding of COVID-19 vaccination hesitancy and identifies key population groups with higher vaccination hesitancy. As the Canadian COVID-19 vaccination effort continues, policymakers may focus outreach, education, and other efforts on these groups, which also represent groups with higher risks for contracting and dying from COVID-19. Furthermore, Canada would need to vaccinate virtually the entire population to reach herd immunity due to its relatively low infection level, and a high vaccination hesitancy would be a major hurdle to achieving that.

SARS-CoV-2 Seroprevalence in 12 Cities of India from July-December 2020

ObjectivesWe sought to understand the spread of SARS-CoV-2 infection in urban India, which has surprisingly low COVID-19 deaths. DesignCross-sectional and trend analyses of seroprevalence in self-referred test populations, and of reported cases and COVID mortality data. Participants448,518 self-referred individuals using a nationwide chain of private laboratories with central testing of SARS-CoV-2 antibodies and publicly available case and mortality data. Setting12 populous cities with nearly 92 million total population. Main outcome measuresSeropositivity trends and predictors (using a Bayesian geospatial model) and prevalence derived from mortality data and infection fatality rates (IFR). ResultsFor the whole of India, 31% of the self-referred individuals undergoing antibody testing were seropositive for SARS-CoV-2 antibodies. Seropositivity was higher in females (35%) than in males (30%) overall and in nearly every age group. In these 12 cities, seroprevalence rose from about 18% in July to 41% by December, with steeper increases at ages <20 and 20-44 years than at older ages. The "M-shaped" age pattern is consistent with intergenerational transmission. Areas of higher childhood measles vaccination in earlier years had lower seropositivity. The patterns of increase in seropositivity and in peak cases and deaths varied substantially across cities. In Delhi, death rates and cases first peaked in June and again in November; Chennai had a single peak in July. Based local IFRs and COVID deaths (adjusted for undercounts), we estimate that 43%-65% of adults above age 20 had been infected (range of mid-estimates of 12%-77%) corresponding 26 to 36 million infected adults in these cities, or an average of 9-12 infected adults per confirmed case. ConclusionEven with relatively low death rates, the large cities of India had remarkably high levels of SARS-CoV-2 infection. Vaccination strategies need to consider widespread intergenerational transmission.

SARS-Cov-2 testing in the United Arab Emirates: Population Attitudes and Beliefs.

ObjectivesThe United Arab Emirates responded to the SARS-COV-2 pandemic and widely implemented test-and-trace strategy. In this cross-sectional questionnaire-based study 531 subjects presenting for SARS-COV-2 testing were recruited to study populations beliefs and choices regarding testing and were compared to 156 who never been tested. ResultsThe community uptake in Abu Dhabi Emirate reached 90% (average of 68% overall). In the great majority it was self-motivated as 6% only had doctor referral. Those who had not taken a test were younger in age (p < 0.001), more likely performing activities such as shopping and eating out (p = 0.001), have a medical illness (p < 0.0001), and working from home (p = 0.005). The tested group reported significantly more agreement with the statement, if someone had negative result no need to stay home or wear mask. In conclusion, SARS-COV-2 testing had extensive coverage and high acceptability in the UAE. Acting on concluded beliefs and attitude are key to ensure the testing coverage efficiency and public empowerment.

A national study of self-reported COVID symptoms during the first viral wave in Canada

ImportanceAccurate understanding of COVID pandemic during the first viral wave in Canada could help prepare for future epidemic waves. ObjectiveTo track the early course of the pandemic by examining self-reported COVID symptoms over time before testing became widely available. DesignAdults from the nationally representative Angus Reid Forum were randomly invited to complete an online survey in May/June 2020. The study is a part of the Action to Beat Coronavirus antibody testing study. SettingA 20-item internet survey. Participants14,408 adults age 18 years of age. ExposuresThe months that respondents and any household members first experienced various respiratory, neurological, sleep, skin or gastric symptoms. Main Outcomes and Measure"COVID symptom-positive," defined as fever (or fever with hallucinations) plus at least one of difficulty breathing, a dry severe cough, loss of smell or "COVID toe." ResultsIn total, 14,408 panel members (48% male and 52% female) completed the survey. Despite overrepresentation of higher levels of education, the prevalence of obesity, smoking, diabetes and hypertension were similar to national census and health surveys. A total of 811 (5.6%) were COVID symptom-positive; highest rates were at ages 18-44 years (8.3% among), declining at older ages. Females had higher odds of reporting COVID symptoms (OR = 1.32, 95%CI 1.11 - 1.56) as did visible minorities (OR = 1.74, 1.29 - 2.35). COVID symptom positivity for respondents and their household members peaked in March (OR = 1.93, 95% CI = 1.59 - 2.34 compared to earlier months). Conclusions and RelevanceThis study enhances our current understanding of the progression of the COVID epidemic in Canada, with few laboratory-confirmed cases in January and February, peaking in April. The results suggest substantial viral transmission in March, before widespread testing began, and a gradual decline in cases since May.

Determinants of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey

In April 2020, the first-ever nationally representative survey in Canada polled 4,240 adults age 18 years and older about their COVID experience in March, early in the epidemic. We examined determinants of COVID symptoms, defined as fever plus difficulty breathing/shortness of breath, dry cough so severe that it disrupts sleep, and/or loss of sense of smell; and testing for SARS-CoV-2 by respondents and/or household members. About 8% of Canadians reported that they and/or one or more household members experienced COVID symptoms. Symptoms were more common in younger than older adults, and among visible minorities. Overall, only 3% of respondents and/or household members reported testing for SARS-CoV-2. Being tested was associated with having COVID symptoms, Indigenous identity, and living in Quebec. Periodic nationally representative surveys--including high-risk older populations--of symptoms, as well as SARS-CoV-2 antibodies, are required in many countries to understand the pandemic and prepare for the future.