SARS-CoV-2-The Role of Natural Immunity: A Narrative Review

Protection of Omicron Sub-Lineage Infection Against Reinfection with Another Omicron Sub-Lineage: Systematic Review, Meta-Analysis, and Meta-Regression - Worldwide, 2022-2023

What is already known about this topic?

Both the decline in immunity over time and the evolution of the virus play a role in the level of protection offered by a prior infection.

What is added by this report?

Point estimates indicated variations in protection levels based on the initial infecting variant and the reinfecting variant. There was a consistent correlation between real-world protection, antigenic distance, and humoral immunity levels. Specifically, shorter antigenic distances and higher humoral immunity levels corresponded to enhanced real-world protection.

What are the implications for public health practice?

Our findings suggest that virological and immunological studies could help identify and assess the epidemic risk posed by new variants before they become dominant. Prompt incorporation of the latest variants into the antigen components of the coronavirus disease 2019 (COVID-19) vaccines can significantly contribute to effective epidemic prevention and control measures.

Protective effectiveness of previous infection against subsequent SARS-Cov-2 infection: systematic review and meta-analysis

Background

The protective effectiveness provided by naturally acquired immunity against SARS-CoV-2 reinfection remain controversial.

Objective

To systematically evaluate the protective effect of natural immunity against subsequent SARS-CoV-2 infection with different variants.

Methods

We searched for related studies published in seven databases before March 5, 2023. Eligible studies included in the analysis reported the risk of subsequent infection for groups with or without a prior SARS-CoV-2 infection. The primary outcome was the overall pooled incidence rate ratio (IRR) of SARS-CoV-2 reinfection/infection between the two groups. We also focused on the protective effectiveness of natural immunity against reinfection/infection with different SARS-CoV-2 variants. We used a random-effects model to pool the data, and obtained the bias-adjusted results using the trim-and-fill method. Meta-regression and subgroup analyses were conducted to explore the sources of heterogeneity. Sensitivity analysis was performed by excluding included studies one by one to evaluate the stability of the results.

Results

We identified 40 eligible articles including more than 20 million individuals without the history of SARS-CoV-2 vaccination. The bias-adjusted efficacy of naturally acquired antibodies against reinfection was estimated at 65% (pooled IRR = 0.35, 95% CI = 0.26-0.47), with higher efficacy against symptomatic COVID-19 cases (pooled IRR = 0.15, 95% CI = 0.08-0.26) than asymptomatic infection (pooled IRR = 0.40, 95% CI = 0.29-0.54). Meta-regression revealed that SARS-CoV-2 variant was a statistically significant effect modifier, which explaining 46.40% of the variation in IRRs. For different SARS-CoV-2 variant, the pooled IRRs for the Alpha (pooled IRR = 0.11, 95% CI = 0.06-0.19), Delta (pooled IRR = 0.19, 95% CI = 0.15-0.24) and Omicron (pooled IRR = 0.61, 95% CI = 0.42-0.87) variant were higher and higher. In other subgroup analyses, the pooled IRRs of SARS-CoV-2 infection were statistically various in different countries, publication year and the inclusion end time of population, with a significant difference (p = 0.02, p < 0.010 and p < 0.010), respectively. The risk of subsequent infection in the seropositive population appeared to increase slowly over time. Despite the heterogeneity in included studies, sensitivity analyses showed stable results.

Conclusion

Previous SARS-CoV-2 infection provides protection against pre-omicron reinfection, but less against omicron. Ongoing viral mutation requires attention and prevention strategies, such as vaccine catch-up, in conjunction with multiple factors.

Blaming the unvaccinated during the COVID-19 pandemic: the roles of political ideology and risk perceptions in the USA

Individuals unvaccinated against COVID-19 (C19) experienced prejudice and blame for the pandemic. Because people vastly overestimate C19 risks, we examined whether these negative judgements could be partially understood as a form of scapegoating (ie, blaming a group unfairly for an undesirable outcome) and whether political ideology (previously shown to shape risk perceptions in the USA) moderates scapegoating of the unvaccinated. We grounded our analyses in scapegoating literature and risk perception during C19. We obtained support for our speculations through two vignette-based studies conducted in the USA in early 2022. We varied the risk profiles (age, prior infection, comorbidities) and vaccination statuses of vignette characters (eg, vaccinated, vaccinated without recent boosters, unvaccinated, unvaccinated-recovered), while keeping all other information constant. We observed that people hold the unvaccinated (vs vaccinated) more responsible for negative pandemic outcomes and that political ideology moderated these effects: liberals (vs conservatives) were more likely to scapegoat the unvaccinated (vs vaccinated), even when presented with information challenging the culpability of the unvaccinated known at the time of data collection (eg, natural immunity, availability of vaccines, time since last vaccination). These findings support a scapegoating explanation for a specific group-based prejudice that emerged during the C19 pandemic. We encourage medical ethicists to examine the negative consequences of significant C19 risk overestimation among the public. The public needs accurate information about health issues. That may involve combating misinformation that overestimates and underestimates disease risk with similar vigilance to error.

Antibodies against SARS-CoV-2 in unvaccinated children hospitalized with COVID-19: An observational cohort study of pre-Omicron and Omicron variants era

PURPOSE

This study aimed to investigate the antibodies against SARS-CoV-2 in children hospitalized due to COVID-19 during the era of pre-Omicron and Omicron variants.

METHODS

This was a retrospective observational study conducted at a tertiary academic medical center in Thailand between June 2021 and August 2022. We collected the data of children aged under 18-year who were hospitalized from SARS-CoV-2 infection. After hospital discharge, we scheduled clinical follow-up 60 to 90 days post-infection clinical follow-up. We measured antibodies against SARS-CoV-2 anti-spike protein receptor-binding domain in the serum during a follow-up visit and compared the mean difference of antibody levels between children infected with COVID-19 during the pre-Omicron and Omicron eras.

RESULTS

A total of 119 children enrolled into the study. There were 58 and 61 children hospitalized due to COVID-19 during pre-Omicron and Omicron era, respectively. The median (interquartile range, IQR) of SARS-CoV-2 antibodies in all cases was 206.1 (87.9-424.1) U/mL at follow-up. Children infected during pre-Omicron had SARS-CoV-2 antibody levels at follow-up higher than children infected during Omicron era [mean difference 292.57 U/mL, 95% CI 53.85-531.28, p = 0.017). There was no difference in SARS-CoV-2 antibody levels between the children based on gender, age, co-morbidities, chest radiograph classification, or diagnosis.

CONCLUSIONS

The antibodies response to SARS-CoV-2 infection was weaker during the Omicron era than previous variant of concern. Immunization strategies and policies should be implemented in children even if they had been previously infected.

Persons with HIV Develop Spike-Specific Lymph Node Germinal Center Responses following SARS-CoV-2 Vaccination

COVID-19 disproportionately affects persons with HIV (PWH) in worldwide locations with limited access to SARS-CoV-2 vaccines. PWH exhibit impaired immune responses to some, but not all, vaccines. Lymph node (LN) biopsies from PWH demonstrate abnormal LN structure, including dysregulated germinal center (GC) architecture. It is not clear whether LN dysregulation prevents PWH from mounting Ag-specific GC responses in the draining LN following vaccination. To address this issue, we longitudinally collected blood and draining LN fine needle aspiration samples before and after SARS-CoV-2 vaccination from a prospective, observational cohort of 11 PWH on antiretroviral therapy: 2 who received a two-dose mRNA vaccine series and 9 who received a single dose of the Ad26.COV2.S vaccine. Following vaccination, we observed spike-specific Abs, spike-specific B and T cells in the blood, and spike-specific GC B cell and T follicular helper cell responses in the LN of both mRNA vaccine recipients. We detected spike-specific Abs in the blood of all Ad26.COV2.S recipients, and one of six sampled Ad26.COV2.S recipients developed a detectable spike-specific GC B and T follicular helper cell response in the draining LN. Our data show that PWH can mount Ag-specific GC immune responses in the draining LN following SARS-CoV-2 vaccination. Due to the small and diverse nature of this cohort and the limited number of available controls, we are unable to elucidate all potential factors contributing to the infrequent vaccine-induced GC response observed in the Ad26.COV2.S recipients. Our preliminary findings suggest this is a necessary area of future research.

The Prevalence of COVID-19 in Europe by the End of November 2022: A Cross-Sectional Study

Background The world has been affected differently by the coronavirus disease 2019 (COVID-19), and Europe reaped the largest number of cases and deaths. Moreover, COVID-19 statistics are dynamic. Objectives The current study aimed to use COVID-19 data to examine the COVID-19 prevalence in Europe by the end of November 2022 and compare the findings globally. Methods The primary data on COVID-19 for each European country were obtained from the "Worldometer" website. The data include the cumulative incidence of COVID-19 per country, the cumulative number of deaths, the total number of tests performed, the number of cases per million population, the number of deaths per million, the number of tests per million, and the total population. The case-fatality rate was calculated (number of deaths/number of cases). In addition, the median age and the vaccination coverage rate (people who received two doses) for each European country were extracted from the "United Nations" website and the "Our World in Data" website, respectively. To compare European countries to the globe, COVID-19 data for each continent were obtained. The analysis of variance (ANOVA) test was used to compare variances across the means of the four parts of Europe based on the geographic division. An independent sample t-test was also used to compare the means between the European Union (EU) states and non-EU states. The Spearman correlation coefficient was used to determine the relationship between different variables across Europe. Results As of December 1, 2022, about 648 million COVID-19 cases and 6.6 million deaths have been recorded worldwide. Europe accounted for nearly 36.8% and 29.5% of all cases and deaths, respectively. Based on the number of deaths per million, Europe was the most affected continent after South America. Nearly 6.8 billion tests have been conducted worldwide, 41% done in Europe; 43 European countries have performed tests more than their population. However, COVID-19 statistics were inconsistent across the four parts of Europe. A significant difference was noticed between Eastern Europe and others, especially Northern Europe and Western Europe. By affiliation with the EU, there was no significant difference. For global comparison, the mean deaths per million, the mean cases per million, and the mean tests per population for European countries were higher than those of the world's countries, although they recorded a lower mean case-fatality rate (CFR). Thirteen European countries were among the 15 most affected countries worldwide based on the number of deaths per million, most located in Eastern and Southern Europe. The number of cases and the number of deaths were significantly proportional to the number of tests performed. Conclusions By the end of November 2022, Europe had the most cases of COVID-19, the most deaths, and the most tests performed, even though it accounts for 9.4% of the world's population. However, COVID-19 data were inconsistent across the four parts of Europe, especially between Eastern Europe and others. Given the natural immunity acquired during the three years and the excellent vaccine coverage in Europe, it is essential to reconsider the definition of a suspected case and establish more specific criteria for testing.

COVID-19 Statistics in the Arab World by the End of October 2022: A Cross-Sectional Study

Background The coronavirus disease 2019 (COVID-19) has affected almost all world countries, including all 22 Arab countries. However, over the last 34 months, the world has suffered from the pandemic unevenly, and COVID-19 statistics are dynamic. Objectives The current study aimed to use COVID-19 data to examine COVID-19 statistics (including the number of cases/deaths/tests) in Arab countries by the end of October 2022 and compare the findings with global statistics. This study was also used to determine the extent to which statistics vary across Arab countries. Methods The primary data on COVID-19 for each Arab country were obtained from the "Worldometer" website. The data include the cumulative incidence of COVID-19 per country, the cumulative number of deaths, the total number of tests performed, the number of cases per million population, the number of deaths per million, the number of tests per million, and the total population. The case-fatality rate (CFR) was calculated (number of deaths/number of cases). In addition, the median age for each Arab country was extracted from the United Nations website. The rate of vaccination coverage (people who received two doses) was extracted from the "Our World in Data" website. COVID-19 statistics were further analyzed in Arab countries in Asia compared to those in Africa at the end of 2020, 2021, and October 2022. To compare the Arab countries to the globe, COVID-19 data for each continent were obtained. The Spearman correlation coefficient was used to determine the relationship between different variables across Arab countries. Results As of November 1, 2022, about 636 million COVID-19 cases and 6.6 million deaths had been recorded worldwide. Arab countries accounted for nearly 2.21% and 2.62% of all cases and deaths, respectively. In general, the mean deaths per million and the mean cases per million for Arab countries were lower than those of the world's countries, although Arab countries recorded a higher mean case-fatality rate. Alternatively, Arab countries in aggregate recorded fewer deaths per million (381) than the world (830). However, statistics across Arab countries have been inconsistent; Arab countries in Africa were less affected. Arab countries have performed approximately 359 million tests (5.29% of all tests), 93% of which were performed by Arab countries in Asia. Moreover, 54.4% of all tests were performed in the United Arab Emirates. Yemen, Somalia, Sudan, Algeria, Syria, Comoros, and Djibouti were the least affected Arab countries based on the number of deaths per million. With the exception of Comoros, these countries were among the least vaccinated in the Arab world. Conclusions In general, Arab countries have been less affected by the COVID-19 pandemic than the rest of the world. However, statistics vary across Arab countries, especially regarding the number of tests performed. Given the natural immunity acquired during the three years and the relatively good vaccine coverage in the Arab world, it is important to reconsider the definition of a suspected case and establish more specific criteria for testing.