Herd immunity induced by COVID-19 vaccination programs and suppression of epidemics caused by the SARS-CoV-2 Delta variant in China

Intention to Vaccinate against COVID-19 in Adolescents: A Systematic Review

BACKGROUND

Multiple COVID-19 vaccines have been approved for use in adolescents; these vaccines play a critical role in limiting the transmission and impact of COVID-19. This systematic review aims to summarize the willingness of adolescents aged 10 to 19 years to receive the COVID-19 vaccination and the factors influencing their decision.

METHODS

A search of literature published between January 2018 and August 2022 was performed in Medline©, EMBASE©. and CINAHL© electronic databases. Studies published in English that assessed adolescents' intentions to receive the COVID-19 vaccine were included. Qualitative studies and those unrelated to the COVID-19 vaccine were excluded. The study was conducted based on the PRISMA guidelines.

RESULTS

Of the 1074 articles retrieved, 13 were included in the final review. Most studies were conducted in the US (n = 3) and China (n = 3). The pooled prevalence of COVID-19 vaccine acceptance among adolescents was 63% (95% CI: 52-73%). Factors influencing intent to vaccinate were divided into five categories: "Socio-demographic determinants"; "Communication about COVID-19 pandemic and vaccination"; "COVID-19 vaccine and related issues"; "COVID-19 infection and related issues" and "Other determinants". The enablers were sociodemographic factors including older age, higher education level, good health perception, and parental norms in terms of parental vaccination acceptance; perceived vaccine effectiveness and safety; a desire to protect themselves and others; recent vaccination; and anxiety. The barriers were concerns over vaccine effectiveness, safety, and long-term side effects; low perceived necessity and risk of infection; and needle phobia.

CONCLUSIONS

This review highlighted that adolescents' intent to vaccinate is driven by a desire to protect themselves and others. However, concerns over vaccine effectiveness, safety, and long-term side effects hinder COVID-19 vaccine uptake. To improve vaccination acceptance, policymakers should address adolescents' concerns via more targeted public health messaging, while schools should leverage peer norms to positively influence vaccination intent.

Comparison of Immunogenicity and Reactogenicity of Five Primary Series of COVID-19 Vaccine Regimens against Circulating SARS-CoV-2 Variants of Concern among Healthy Thai Populations

To compare immunogenicity and reactogenicity of five COVID-19 vaccine regimens against wild-type SARS-CoV-2 and variants of concern (VoCs) among Thai populations, a prospective cohort study was conducted among healthy participants aged ≥18 years who had never been infected with COVID-19 and were scheduled to get one of the five primary series of COVID-19 vaccine regimens, including CoronaVac/CoronaVac, AZD1222/AZD1222, CoronaVac/AZD1222, AZD1222/BNT162b2, and BNT162b2/BNT162b2. Anti-receptor binding domain (anti-RBD-WT) IgG and neutralizing antibody (NAb-WT) against wild-type SARS-CoV-2 were measured at pre-prime, post-prime, and post-boost visits. NAb against VoCs (NAb-Alpha, NAb-Beta, NAb-Delta, and NAb-Omicron) were assessed at the post-boost visit. Adverse events (AEs) following vaccination were recorded. A total of 901 participants (CoronaVac/CoronaVac: 332, AZD1222/AZD1222: 221, CoronaVac/AZD1222: 110, AZD1222/BNT162b2: 128, and BNT162b2/BNT162b2: 110) were enrolled. Anti-RBD-WT IgG and NAb-WT levels increased substantially after each vaccine dose. At the post-boost visit, BNT162b2/BNT162b2 induced the highest GMC of anti-RBD-WT IgG level (1698 BAU/mL), whereas AZD1222/BNT162b2 induced the highest median NAb-WT level (99% inhibition). NAb levels against VoCs, particularly the Omicron strain, were markedly attenuated for all vaccine regimens (p < 0.001). Overall, no serious AEs following vaccination were observed. All five primary series of COVID-19 vaccine regimens were well-tolerated and elicited robust antibody responses against wild-type SARS-CoV-2 but had attenuated responses against VoCs, particularly the Omicron strain, among healthy Thai populations.

The whole-of-society approach of mass COVID-19 vaccination in China: a qualitative study

BACKGROUND

Many countries have an inefficient vaccination system, which hinders global exit from the COVID-19 pandemic. It is vital to summarize COVID-19 vaccination practices in countries with high vaccination coverage and provide implications for other countries. This study aimed to investigate China's COVID-19 vaccination system and to summarize its implementation experience from a health system perspective.

METHODS

We conducted key informant interviews in five representative cities of China in late 2021. Guided by the health systems framework proposed by WHO, we developed our interview guidelines which included seven building blocks-leadership and governance, health workforce, vaccination service delivery, vaccination mobilization and communication, financing, access to vaccines, and information systems. Semi-structured interviews and COVID-19 vaccination policy documents were collected and coded using a thematic analysis approach.

RESULTS

A total of 61 participants (nine vaccination programme directors of the local Center for Disease Control and Prevention, four government staff and 48 vaccination service workers) were interviewed. We found that China adopted a whole-of-society approach with adequate government engagement and linked health and non-health sectors to promote COVID-19 vaccination. Key measures included the collaboration of multiple systems and departments from a governance perspective, allocating sufficient health workers and resources, large-scale vaccination mobilization and communication, expansion of vaccine financing channels, localized production and digital information systems. With the vaccination system strengthening, the two-doses vaccination coverage reached 89.5% for the total population but relatively lower coverage for older adults as of July 2022.

CONCLUSIONS

Our study highlights the importance of a government-led whole-of-society approach to promote mass vaccination. The low vaccination coverage among older adults should be paid the greatest attention to. The experiences and lessons from China may serve as a reference for other countries.

Challenges of vaccination and herd immunity in COVID-19 and management strategies

Coronavirus disease 2019 (COVID-19), the highly contagious viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread worldwide with millions of cases and more than 5 million deaths to date. SARS-CoV-2 has caused serious damage all over the world with many countries experiencing the third or the fourth wave of the viral disease outbreaks, mainly due to the emergence of mutant variants. Those who unvaccinated remain most vulnerable to COVID-19 and its variants. COVID-19 vaccination, along with prevention strategies, is a critical measure to defense against the disease. COVID-19 vaccination can reduce the spread of virus and help protect susceptible population. Although herd immunity might not be realized solely by vaccination, COVID-19 vaccines have been proved to be effective in reducing the risk of severe disease, hospitalization, and even death. It is recommended that people get vaccinated as soon as they are eligible. This review summarizes the recent SARS-CoV-2 variants that brought challenges for vaccination and herd immunity and discusses promising management strategies.

COVID-19 vaccine acceptance and hesitancy among the general population of Pakistan: a population-based survey

OBJECTIVES

This study aims to determine the COVID-19 vaccination coverage and the factors associated with vaccine acceptance and hesitancy in the general population of Pakistan.

SETTING

This population-based study covers all major areas of Pakistan, including Sindh, Punjab, Khyber Pakhtunkhwa and Baluchistan provinces and the capital Islamabad.

PARTICIPANTS

A total of 541 male and female Pakistani adults above 18 years were interviewed to determine the COVID-19 vaccination coverage and understand the factors associated with vaccine acceptance and hesitancy.

OUTCOME

The outcome was COVID-19 vaccination status (not vaccinated or vaccinated).

RESULTS

Of 541 participants, 227 (41.96%) were non-vaccinated and 314 (58.04%) were vaccinated. Two-thirds of the participants from both the non-vaccinated and vaccinated groups (185 (81.50%) vs 236 (75.16%), p=0.008) reside in Sindh. Nearly one-third of participants from both groups were ever infected with COVID-19 (77 (33.92%) and 90 (28.66%)). The odds of COVID-19 vaccination among the age group 34-42 years were 1.75 times higher (95% CI 1.35 to 2.09, p=0.008) than the other age groups. The odds of COVID-19 vaccination among those with COVID-19 ever-infected family members were 1.87 times higher (95% CI 1.56 to 2.34, p=0.032) than those with uninfected family members.

CONCLUSIONS

Targeted interventions for subsets of populations reluctant to vaccination can improve vaccine coverage. Moreover, advocacy and explaining the public health benefits of vaccination can enhance the coverage in Pakistan.

The impact of the COVID-19 pandemic on college students in USA: Two years later

Coronavirus disease 19 (COVID-19) has posed an unprecedented public health challenge for most countries, and the repeated outbreaks of this disease have created a largest disruption of education systems. The intent of this work was to examine the intersection of COVID-19 fear and mental health consequences among college students in Northern Michigan, a region of the U.S. severely affected by the pandemic. This study was conducted from January 17 to February 25, 2022, two years later since the outbreak of the pandemic, and 151 college students (female, 76) were involved. Participants' potential psychological symptoms, anxiety, happiness, learning difficulty, and demographic information were surveyed. We have three main findings. First, 60.3% of students had tested positive for COVID-19, and more female than male students were affected (female, 69.7%; male, 50.7%). Second, there was a high prevalence of mental problems among college students, with 95.7% of the sample experiencing moderate or severe mood disorders. Third, respondents' education was severely affected by the pandemic, averaging a score of 7.6 on a scale of 10 when asked how much their learning quality was affected. They showed increased fear, stress, and decreased happiness, and these were associated with their learning quality change. Given the impact would be far-reaching, not only college students' mental health but also their learning difficulties should be monitored during the pandemic. These findings are alarming and timely, and their implications are discussed.

Epidemiological Characteristics of COVID-19 Outbreak in Yangzhou, China, 2021

Objective

Epidemiological characteristics of COVID-19 outbreak in Yangzhou city caused by the highly contagious Delta variant strain of SARS-CoV-2 virus were investigated in this retrospective descriptive study to provide prevention and control guidelines for outbreaks in the future.

Methods

All the epidemiological data used in this study were collected manually from the official website of the Yangzhou Municipal Health Committee from 28 July to 26 August 2021, and then were analyzed systematically and statistically in this study.

Results

A total of 570 COVID-19 cases were reported during the short-term outbreak in Yangzhou City. The ages of infected individuals ranged from 1 to 90 years with the average age at 49.47 ± 22.69 years. As for gender distributions, the ratio of male- to-female patients was 1:1.36 (242:328). Geographic analysis showed that 377 patients (66.1%) were in Hanjiang District while 188 patients (33.0%) were in Guangling District. Clinical diagnosis showed that 175 people (30.7%) had mild symptoms, 385 people were in moderate conditions (67.5%), and 10 people were in severe situations (1.8%). Significant age differences were found among the three groups (P < 0.001). However, no significant difference was identified in terms of gender ratio (P > 0.05). Based on the transmission chain formed by 6 generations of infected persons with a clear transmission relationship, the age showed a gradually decreasing trend, while the median time of diagnosis in 2 adjacent generations was 3 days. In addition, the estimated basic reproduction number R 0 of the Delta variant was 3.3651 by the classical Susceptible, Infectious, and/or Recovered (SIR) model.

Conclusion

The Delta variant of SARS-CoV-2 was highly infectious and has obvious clustering characteristics during the Yangzhou outbreak in China.

Face masking and COVID-19: potential effects of variolation on transmission dynamics

Face masks do not completely prevent transmission of respiratory infections, but masked individuals are likely to inhale fewer infectious particles. If smaller infectious doses tend to yield milder infections, yet ultimately induce similar levels of immunity, then masking could reduce the prevalence of severe disease even if the total number of infections is unaffected. It has been suggested that this effect of masking is analogous to the pre-vaccination practice of variolation for smallpox, whereby susceptible individuals were intentionally infected with small doses of live virus (and often acquired immunity without severe disease). We present a simple epidemiological model in which mask-induced variolation causes milder infections, potentially with lower transmission rate and/or different duration. We derive relationships between the effectiveness of mask-induced variolation and important epidemiological metrics (the basic reproduction number and initial epidemic growth rate, and the peak prevalence, attack rate and equilibrium prevalence of severe infections). We illustrate our results using parameter estimates for the original SARS-CoV-2 wild-type virus, as well as the Alpha, Delta and Omicron variants. Our results suggest that if variolation is a genuine side-effect of masking, then the importance of face masks as a tool for reducing healthcare burdens from COVID-19 may be under-appreciated.

Passive Immunotherapy Against SARS-CoV-2: From Plasma-Based Therapy to Single Potent Antibodies in the Race to Stay Ahead of the Variants

The COVID-19 pandemic is now approaching 2 years old, with more than 440 million people infected and nearly six million dead worldwide, making it the most significant pandemic since the 1918 influenza pandemic. The severity and significance of SARS-CoV-2 was recognized immediately upon discovery, leading to innumerable companies and institutes designing and generating vaccines and therapeutic antibodies literally as soon as recombinant SARS-CoV-2 spike protein sequence was available. Within months of the pandemic start, several antibodies had been generated, tested, and moved into clinical trials, including Eli Lilly's bamlanivimab and etesevimab, Regeneron's mixture of imdevimab and casirivimab, Vir's sotrovimab, Celltrion's regdanvimab, and Lilly's bebtelovimab. These antibodies all have now received at least Emergency Use Authorizations (EUAs) and some have received full approval in select countries. To date, more than three dozen antibodies or antibody combinations have been forwarded into clinical trials. These antibodies to SARS-CoV-2 all target the receptor-binding domain (RBD), with some blocking the ability of the RBD to bind human ACE2, while others bind core regions of the RBD to modulate spike stability or ability to fuse to host cell membranes. While these antibodies were being discovered and developed, new variants of SARS-CoV-2 have cropped up in real time, altering the antibody landscape on a moving basis. Over the past year, the search has widened to find antibodies capable of neutralizing the wide array of variants that have arisen, including Alpha, Beta, Gamma, Delta, and Omicron. The recent rise and dominance of the Omicron family of variants, including the rather disparate BA.1 and BA.2 variants, demonstrate the need to continue to find new approaches to neutralize the rapidly evolving SARS-CoV-2 virus. This review highlights both convalescent plasma- and polyclonal antibody-based approaches as well as the top approximately 50 antibodies to SARS-CoV-2, their epitopes, their ability to bind to SARS-CoV-2 variants, and how they are delivered. New approaches to antibody constructs, including single domain antibodies, bispecific antibodies, IgA- and IgM-based antibodies, and modified ACE2-Fc fusion proteins, are also described. Finally, antibodies being developed for palliative care of COVID-19 disease, including the ramifications of cytokine release syndrome (CRS) and acute respiratory distress syndrome (ARDS), are described.

COVID-19 Vaccine Perceptions, Intentions, and Uptake Among Young Adults in the United States: Prospective College-Based Cohort Study

Background

Uptake of the COVID-19 vaccine among US young adults, particularly those that belong to racial and ethnic minorities, remains low compared to their older peers. Understanding vaccine perceptions and their influence on vaccination uptake among this population remains crucial to achieving population herd immunity.

Objective

We sought to study perceptions of COVID-19 vaccines as well as intended and actual vaccine uptake among one population of college students, faculty, and staff.

Methods

As part of a larger study aimed at investigating the dynamics of COVID-19 transmission, serology, and perception on a college campus, participants were asked about their views on the COVID-19 vaccine in February 2021. Vaccination status was assessed by self-report in April 2021. Logistic regression was used to calculate prevalence ratios with marginal standardization.

Results

We found that non-White participants were 25% less likely to report COVID-19 vaccination compared to White participants. Among those who were unvaccinated, Black and other non-White participants were significantly more likely to indicate they were unwilling to receive a COVID-19 vaccine compared to White participants. The most common reason for unwillingness to receive the vaccine was belief that the vaccine approval process was rushed.

Conclusions

There are racial differences in perceptions of the COVID-19 vaccine among young adults, and these differences might differentially impact vaccine uptake among young racial and ethnic minorities. Efforts to increase vaccine uptake among college populations might require campaigns specifically tailored to these minority groups.

Vaccine effectiveness against SARS-CoV-2 transmission to household contacts during dominance of Delta variant (B.1.617.2), the Netherlands, August to September 2021

We estimated SARS-CoV-2 vaccine effectiveness against onward transmission by comparing secondary attack rates among household members for vaccinated and unvaccinated index cases, based on source and contact tracing data collected when the Delta variant was dominant. Effectiveness of full vaccination of the index case against transmission to unvaccinated and fully vaccinated household contacts, respectively, was 63% (95% confidence interval (CI): 46–75) and 40% (95% CI: 20–54), in addition to the direct protection of vaccination of contacts against infection.

Immune Responses against SARS-CoV-2-Questions and Experiences

Understanding immune reactivity against SARS-CoV-2 is essential for coping with the COVID-19 pandemic. Herein, we discuss experiences and open questions about the complex immune responses to SARS-CoV-2. Some people react excellently without experiencing any clinical symptoms, they do not get sick, and they do not pass the virus on to anyone else ("sterilizing" immunity). Others produce antibodies and do not get COVID-19 but transmit the virus to others ("protective" immunity). Some people get sick but recover. A varying percentage develops respiratory failure, systemic symptoms, clotting disorders, cytokine storms, or multi-organ failure; they subsequently decease. Some develop long COVID, a new pathologic entity similar to fatigue syndrome or autoimmunity. In reality, COVID-19 is considered more of a systemic immune-vascular disease than a pulmonic disease, involving many tissues and the central nervous system. To fully comprehend the complex clinical manifestations, a profound understanding of the immune responses to SARS-CoV-2 is a good way to improve clinical management of COVID-19. Although neutralizing antibodies are an established approach to recognize an immune status, cellular immunity plays at least an equivalent or an even more important role. However, reliable methods to estimate the SARS-CoV-2-specific T cell capacity are not available for clinical routines. This deficit is important because an unknown percentage of people may exist with good memory T cell responsibility but a low number of or completely lacking peripheral antibodies against SARS-CoV-2. Apart from natural immune responses, vaccination against SARS-CoV-2 turned out to be very effective and much safer than naturally acquired immunity. Nevertheless, besides unwanted side effects of the currently available vector and mRNA preparations, concerns remain whether these vaccines will be strong enough to defeat the pandemic. Altogether, herein we discuss important questions, and try to give answers based on the current knowledge and preliminary data from our laboratories.