COVID-19 Vaccine Challenges in Developing and Developed Countries

The coronavirus disease 2019 (COVID-19) pandemic has led to significant psychological and economical distress. Within a year after COVID-19 was declared a pandemic, several vaccines against COVID-19 were approved for emergency use. The journey from vaccine discovery to global herd immunity against COVID-19 continues to present significant challenges revolving around its development, affordability, accessibility, and acceptability at both a country level and an individual level. The main challenge faced by developed countries is the acceptability of the COVID-19 vaccine and the main challenge faced by developing countries is the affordability and accessibility of the COVID-19 vaccine.

A comparative analysis on the safety and efficacy of Covaxin versus other vaccines against COVID-19: a review

Since the identification of the genomic sequence of SARS-CoV-2, an unprecedented effort is being made until this date for the development of a safe and effective vaccine by pharma companies and laboratories worldwide. To attain herd immunity and quite possibly recover from this pandemic, which has claimed the life of about 4.23 million people, an exceptional effort has been made by the scientific community for the development of a vaccine. Various vaccines have been developed based on different platforms and each of them seems to possess its own merits and demerits based on its safety, immunogenicity, the durability of immunity, dosing schedule, technological platform, and ease of manufacture and transport. Based on these parameters this review aims to critically assess the efficacy of Covaxin and compare it with other vaccines in the WHO EUL list and perform a comparative analysis of COVID-19 vaccines which are in phase 3 and phase 4 of clinical trials. This will help us determine where COVAXIN stands against other vaccines and vaccine candidates based on these parameters which will ultimately help us determine the best vaccine that could potentially eradicate the COVID-19 pandemic.

What to Do in the Next Pandemic Outbreak: Natural Herd Immunity Versus Lockdown (Lessons Learned from COVID-19)

The purpose of this article is to analyse non-pharmaceutical approaches to control pandemics. Currently vaccines are our best hope to control the COVID-19 pandemic, but before the appearance of the first vaccines the available possibilities were much more limited. While most people worldwide were confined to their homes to slow the spread of the new coronavirus, some countries (most notably the United Kingdom) advocated infecting the majority of the community, aiming to achieve what has been called "herd immunity". This article focuses on two non-therapeutic strategies for dealing with deadly viruses and points out their respective problems: natural herd immunity and quarantines/lockdowns. It analyses these strategies from three perspectives: legal, ethical and social. The article concludes that in the absence of therapeutic alternatives (vaccines), short-term lockdowns are necessary, but long-term lockdowns are legally, ethically, socially and financially impossible to sustain.

Great Expectations of COVID-19 Herd Immunity

There is a common preconception that reaching an estimated herd immunity threshold through vaccination will end the COVID-19 pandemic. However, the mathematical models underpinning this estimate make numerous assumptions that may not be met in the real world. The protection afforded by vaccines is imperfect, particularly against asymptomatic infection, which can still result in transmission and propagate pandemic viral spread. Immune responses wane and SARS-COV-2 has the capacity to mutate over time to become more infectious and resistant to vaccine elicited immunity. Human behavior and public health restrictions also vary over time and among different populations, impacting the transmissibility of infection. These ever-changing factors modify the number of secondary cases produced by an infected individual, thereby necessitating constant revision of the herd immunity threshold. Even so, vaccination remains a powerful strategy to slow down the pandemic, save lives, and alleviate the burden on limited health care resources.

A narrative review of emergency use authorization versus full FDA approval and its effect on COVID-19 vaccination hesitancy

COVID-19 pandemic affected the lives of many with its devastating mortality and morbidity. Acquisition of herd immunity is one way to mitigate the spread of infection. Many factors influence the acceptance of vaccination including the regulatory process of the vaccines. This review article will briefly summarize the Emergency Use Authorization, Full FDA Approval process and highlight how the key factors affecting the vaccination hesitancy, are being influenced by the lack of Full FDA Approval.

High Incidence of SARS-CoV-2 Within Incarcerated Populations and Possible Implications for Herd Immunity

Controlling the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been challenging in the community and prison systems. Where herd immunity lies for this virus is unknown, although estimates have ranged from 60% to 80%. Since the start of the pandemic, there have been multiple SARS-CoV-2 outbreaks within U.S. prison systems, which may provide more insight on where true herd immunity lies. We reviewed data from the California Department of Corrections and Rehabilitation to investigate the cumulative incidence of infection and found levels in 14 (40%) of 35 prisons were >60%. These data and existing literature suggest that in prison environments, prevalence of immunity often needs to reach >70% before transmission slows. Similar levels may be needed in the general population before transmission is suppressed.

Bayesian Inference of State-Level COVID-19 Basic Reproduction Numbers across the United States

Although many persons in the United States have acquired immunity to COVID-19, either through vaccination or infection with SARS-CoV-2, COVID-19 will pose an ongoing threat to non-immune persons so long as disease transmission continues. We can estimate when sustained disease transmission will end in a population by calculating the population-specific basic reproduction number ℛ0, the expected number of secondary cases generated by an infected person in the absence of any interventions. The value of ℛ0 relates to a herd immunity threshold (HIT), which is given by 1-1/ℛ0. When the immune fraction of a population exceeds this threshold, sustained disease transmission becomes exponentially unlikely (barring mutations allowing SARS-CoV-2 to escape immunity). Here, we report state-level ℛ0 estimates obtained using Bayesian inference. Maximum a posteriori estimates range from 7.1 for New Jersey to 2.3 for Wyoming, indicating that disease transmission varies considerably across states and that reaching herd immunity will be more difficult in some states than others. ℛ0 estimates were obtained from compartmental models via the next-generation matrix approach after each model was parameterized using regional daily confirmed case reports of COVID-19 from 21 January 2020 to 21 June 2020. Our ℛ0 estimates characterize the infectiousness of ancestral strains, but they can be used to determine HITs for a distinct, currently dominant circulating strain, such as SARS-CoV-2 variant Delta (lineage B.1.617.2), if the relative infectiousness of the strain can be ascertained. On the basis of Delta-adjusted HITs, vaccination data, and seroprevalence survey data, we found that no state had achieved herd immunity as of 20 September 2021.

Providing children with COVID-19 vaccinations is challenging due to lack of data and wide-ranging parental acceptance

Aim

Vaccines are vital to ending the COVID‐19 pandemic and we reviewed the data on vaccinating children, and including them in clinical trials, as most of the activity has focused on adults.

Methods

English and Chinese databases, including PubMed, Elsevier Scopus, Web of Science, CNKI and CQVIP were searched, along with websites such as the World Health Organization and the University of Oxford.

Results

We identified 44 papers and 16 news items about vaccinating children against the virus, published from 10 February 2020 to 14 July 2021. Child vaccination has been slow and only a few countries have included children in Phase II or III clinical trials. The data on children were much more limited than on adults, but most children were asymptomatic or had mild symptoms and some deaths had been recorded. More clinical trials are needed to assess the safety and efficacy of vaccinating children, as higher vaccination levels can help to build up herd immunity. The percentage of parents willing to vaccinate their children against the virus ranged from 48.2% to 72.6%, with much lower rates for letting them participate in clinical trials.

Conclusion

Vaccines should be offered to children as soon as their safety and efficacy are established.

Fall 2021 Update: Navigating COVID Vaccination in Tumultuous Times

ABSTRACT

The COVID-19 pandemic and subsequent development of COVID vaccines have resulted in unique challenges for nurses. Nurses are being asked to make recommendations about vaccinations that have only been available since December 2020 even as vaccine information evolves on an almost daily basis. Standards of professional care and a Christian perspective on nursing to help guide nurses' practice in the current climate are discussed in this article. An overview of information and research findings published up to October 31, 2021 about COVID-19 vaccination is given to assist nurses in answering vaccination questions.

Vaccine Hesitancy Is a Barrier to Achieving Equitable Herd Immunity Among Racial Minorities

Introduction: Racial minority groups have been disproportionately affected by the 2019 novel coronavirus disease (COVID-19). Vaccine hesitancy may be a major barrier to achieving equitable herd immunity and must be addressed to reduce the excess morbidity and mortality of COVID-19 in disproportionately affected communities. This study aimed to determine if COVID-19 vaccine hesitancy, and its factors vaccine complacency and confidence, are more prominent among disproportionately affected racial minority groups.

Methods:We collected data from participants aged 18 years or older from the four most populous U.S. states, including New York, California, Florida, and Texas, and Canada. Data were collected using a web-based survey platform. Data are available at http://www.covid19-database.com.

Results:Data from 4,434 participants were included [mean (SD) age = 48.7 (17.2) and 50.4% women]. Vaccine hesitancy was higher in Black, Indigenous (Native American and Indigenous People of Canada, including First Nations, Inuit and Métis), and Latinx compared to White participants, while no difference was found between East Asian and White participants. The group differences in vaccine hesitancy for Indigenous and Black compared to White participants remained after controlling for sociodemographic factors. Determinants of vaccine complacency were equivalent between disproportionately affected racial groups and white participants. Vaccine confidence (i.e., trust in vaccine benefit) was generally lower in all racial groups compared to White participants. Differences in vaccine mistrust comparing Black and East Asian to White participants remained after controlling for sociodemographic factors.

Discussion:Disproportionately affected racial minorities may have higher vaccine hesitancy and lower confidence in COVID-19 vaccines. Public health and other relevant government services should address vaccine hesitancy among racial minorities using a culturally sensitive, community-centered approach to attain equitable herd immunity.

A Survey on the Side Effects of Pfizer/BioNTech COVID-19 Vaccine Among Vaccinated Adults in Saudi Arabia

Background: Pfizer-BioNTech vaccine was the first of all coronavirus disease (COVID) vaccines to be used in Saudi Arabia. There have been over 17 million doses already administered to the general public in order to successfully reach herd immunity.

Objective: The study aimed to explore the side effects of the Pfizer-BioNTech vaccine.

Materials and methods: This is a cross-sectional study comprising a sample of 386 participating adults of different age groups and genders. A validated modified questionnaire was distributed as a Google form to residents of the kingdom via social networking sites from February to March 2021. The questionnaire included questions regarding participants’ socio-demographic details, vaccination details, and symptom analyses items.

Results: The most common to least reported symptoms were local pain (79.3%), fatigue (42%), muscle pain (39.1%), local swelling (27.7%), joint pain (23.1%), headache (21.8%), fever (21.0%), chills (15.5%), local redness (14.8%), nausea (7.3%), with no reports of anaphylaxis, facial paralysis or syncope. There were more side effects after the second dose than the first (p<0.001). Significant predictors of a higher number of side effects after both doses of the vaccine were the female gender ((p<0.001)) and the presence of allergies (p=0.044).

Conclusion: Pfizer/BioNTech vaccination was quite safe with no reported anaphylaxis or serious events. The most common reported side effects were local pain and fatigue. Symptoms began within 24 hours and were mild to moderate in nature with a regressive course, especially after analgesics. More side effects were experienced after the second dose than the first. The significant predictors of side effects were the female gender and a history of allergies.

The SARS-CoV-2 pandemic: remaining uncertainties in our understanding of the epidemiology and transmission dynamics of the virus, and challenges to be overcome

Great progress has been made over the past 18 months in scientific understanding of the biology, epidemiology and pathogenesis of SARS-CoV-2. Extraordinary advances have been made in vaccine development and the execution of clinical trials of possible therapies. However, uncertainties remain, and this review assesses these in the context of virus transmission, epidemiology, control by social distancing measures and mass vaccination and the effect on all of these on emerging variants. We briefly review the current state of the global pandemic, focussing on what is, and what is not, well understood about the parameters that control viral transmission and make up the constituent parts of the basic reproductive number R 0. Major areas of uncertainty include factors predisposing to asymptomatic infection, the population fraction that is asymptomatic, the infectiousness of asymptomatic compared to symptomatic individuals, the contribution of viral transmission of such individuals and what variables influence this. The duration of immunity post infection and post vaccination is also currently unknown, as is the phenotypic consequences of continual viral evolution and the emergence of many viral variants not just in one location, but globally, given the high connectivity between populations in the modern world. The pattern of spread of new variants is also examined. We review what can be learnt from contact tracing, household studies and whole-genome sequencing, regarding where people acquire infection, and how households are seeded with infection since they constitute a major location for viral transmission. We conclude by discussing the challenges to attaining herd immunity, given the uncertainty in the duration of vaccine-mediated immunity, the threat of continued evolution of the virus as demonstrated by the emergence and rapid spread of the Delta variant, and the logistics of vaccine manufacturing and delivery to achieve universal coverage worldwide. Significantly more support from higher income countries (HIC) is required in low- and middle-income countries over the coming year to ensure the creation of community-wide protection by mass vaccination is a global target, not one just for HIC. Unvaccinated populations create opportunities for viral evolution since the net rate of evolution is directly proportional to the number of cases occurring per unit of time. The unit for assessing success in achieving herd immunity is not any individual country, but the world.

Assessing Acceptability of COVID-19 Vaccine Booster Dose among Adult Americans: A Cross-Sectional Study

Given the emergence of breakthrough infections, new variants, and concerns of waning immunity from the primary COVID-19 vaccines, booster shots emerged as a viable option to shore-up protection against COVID-19. Following the recent authorization of vaccine boosters among vulnerable Americans, this study aims to assess COVID-19 vaccine booster hesitancy and its associated factors in a nationally representative sample. A web-based 48-item psychometric valid survey was used to measure vaccine literacy, vaccine confidence, trust, and general attitudes towards vaccines. Data were analyzed through Chi-square (with a post hoc contingency table analysis) and independent-sample t-/Welch tests. Among 2138 participants, nearly 62% intended to take booster doses and the remaining were COVID-19 vaccine booster hesitant. The vaccine-booster-hesitant group was more likely to be unvaccinated (62.6% vs. 12.9%) and did not intend to have their children vaccinated (86.1% vs. 27.5%) compared to their non-hesitant counterparts. A significantly higher proportion of booster dose hesitant individuals had very little to no trust in the COVID-19 vaccine information given by public health/government agencies (55% vs. 12%) compared to non-hesitant ones. The mean scores of vaccine confidence index and vaccine literacy were lower among the hesitant group compared to the non-hesitant group. Compared to the non-hesitant group, vaccine hesitant participants were single or never married (41.8% vs. 28.7%), less educated, and living in a southern region of the nation (40.9% vs. 33.3%). These findings underscore the need of developing effective communication strategies emphasizing vaccine science in ways that are accessible to individuals with lower levels of education and vaccine literacy to increase vaccination uptake.

Immunization against severe acute respiratory syndrome Coronavirus 2: an overview

In the past years, numerous new fatal infections have emerged, including Ebola, Nipah, and Zika viruses, as well as coronaviruses. Recently, infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged in China, and were then transmitted all over the world, causing the coronavirus disease-19 (COVID-19) pandemic, which is transmitted at a higher rate than other diseases caused by coronaviruses. At the time of writing this review, COVID-19 is not contained in most countries in spite of quarantine, physical distancing, and enhanced hygiene measures. In this review, I address different methods for passive and active immunization against this virus, which is known to cause fatal respiratory disease, including natural passive immunization by breast milk, natural active immunization by herd immunization, artificial passive immunization by convalescent plasma or monoclonal antibodies, and artificial active immunization by vaccination. I hope this review will help design a prophylactic approach against outbreaks and pandemics of related coronaviruses in the future.

COVID-19 vaccinations: The unknowns, challenges, and hopes

The entire world has been suffering from the coronavirus disease 2019 (COVID‐19) pandemic since March 11, 2020. More than a year later, the COVID‐19 vaccination brought hope to control this viral pandemic. Here, we review the unknowns of the COVID‐19 vaccination, such as its longevity, asymptomatic spread, long‐term side effects, and its efficacy on immunocompromised patients. In addition, we discuss challenges associated with the COVID‐19 vaccination, such as the global access and distribution of vaccine doses, adherence to hygiene guidelines after vaccination, the emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) variants, and vaccine resistance. Despite all these challenges and the fact that the end of the COVID‐19 pandemic is still unclear, vaccines have brought great hope for the world, with several reports indicating a significant decline in the risk of COVID19‐related infection and hospitalizations.

1.

Vaccination plays a pivotal role in reducing the death toll of the COVID‐19 infection.

2.

The immunity provided by vaccines is still disputable leading to some challenges like the asymptomatic spread; therefore, staying strict to hygiene guidelines is necessary.

3.

Hence, COVID‐19 vaccines' related long‐term side effects are still unknown; cautions should be taken when injected to various individuals of the community.

4.

COVID‐19 vaccines' effectiveness are strongly related to their effect on emergent COVID‐19 variants, but until now approved vaccines can still show some protective effects against new variants.

Reaching Herd Immunity During the SARS-CoV-2 Pandemic: What School Nurses Need to Know

The National Association of School Nurses supports pandemic control efforts. School nurses are advocates for their students, caregivers, school staff, teachers, and school administrators. With a clear understanding of how the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) virus evolves over time and changes transmissibility through mutations, school nurses gain understanding in epidemiologic calculation of herd immunity. To understand why the estimates of herd immunity fluctuate, as often reported in the news, school nurses need to understand how epidemiologist calculate this number. Obtaining herd immunity will protect the most vulnerable in the population. If all countries have access to vaccines and populations choose to receive vaccinations, herd immunity is more likely to be obtained. Equipped with knowledge of how herd immunity is calculated, school nurses are in a position to educate and advocate for the use of vaccines.

On the Need for an Association for Vaccinated Person's Rights

COVID-19 has been more difficult to contain in the United States than in other countries due, in part, to our nation's rootedness in preserving individual freedoms, sometimes in defiance of the need for social accountability for health. With growing evidence that anti-vaccination proponents are increasingly organized, funded, and influential, this editorial argues that the right to health should transcend individual freedoms that have a likely probability of spreading harm to others. An association for vaccinated person's rights, much like ANSR, an association for non-smokers rights, may be needed to counter anti-vaccination rights organizers. Advancing a goal of mostly "vaccinated and fully immunized populations' would make members of such a group 'VIP-ers.'".

Reducing COVID-19 Vaccine Hesitancy by Implementing Organizational Intervention in a Primary Care Setting in Bahrain

Background: Refusal to receive the COVID-19 vaccine or hesitancy is a global threat. Hence, reducing vaccine hesitancy is the next challenge for policymakers and the healthcare system. However, people trust healthcare professionals more than any other source of information. Accordingly, planning for an effective process and competent healthcare professional to elicit and address the patient's concerns is an imperative measure. This quality improvement project aimed to improve physicians’ COVID-19 vaccine advice to reduce vaccine hesitancy.

Methods: The study used judgmental sampling and involved 665 hesitant patients over 19 weeks. The team utilized the Plan-Do-Study-Act method to implement COVID-19 vaccine physicians’ reminders and upgrades physicians’ communication skills to conduct an effective tailored communication that addresses the patient’s concerns toward COVID-19 vaccines. The team used pre-post design to evaluate the impact of counseling on the hesitancy rate of patients before and after the intervention over time. The main outcomes were the percentage of physicians’ COVID-19 vaccine advice for patients and the percentage of hesitancy rate before and after implementation.

Results: There were 665 hesitant patients before intervention. However, after the intervention, the number decreased to 193 patients, and the control chart revealed a reliable process. The percentage of recommendations by physicians has increased from 1% to 51% after 19 weeks of implementation and with a controlled process.

Conclusion: The study has found that rectifying process barriers and upgrading physicians’ skills would improve the COVID-19 vaccine counseling rate and introducing tailored communication would reduce the hesitancy rate. Nevertheless, the study was constrained by a lack of information on the impact of social media and national measures on patients’ decisions. Additional studies with more emphasis on other patients’ behavior determinants are necessary.

Stochastic social behavior coupled to COVID-19 dynamics leads to waves, plateaus, and an endemic state

It is well recognized that population heterogeneity plays an important role in the spread of epidemics. While individual variations in social activity are often assumed to be persistent, that is, constant in time, here we discuss the consequences of dynamic heterogeneity. By integrating the stochastic dynamics of social activity into traditional epidemiological models, we demonstrate the emergence of a new long timescale governing the epidemic, in broad agreement with empirical data. Our stochastic social activity model captures multiple features of real-life epidemics such as COVID-19, including prolonged plateaus and multiple waves, which are transiently suppressed due to the dynamic nature of social activity. The existence of a long timescale due to the interplay between epidemic and social dynamics provides a unifying picture of how a fast-paced epidemic typically will transition to an endemic state.

Does Seeing What Others Do Through Social Media Influence Vaccine Uptake and Help in the Herd Immunity Through Vaccination? A Cross-Sectional Analysis

Widespread acceptance of COVID-19 vaccination is the next major step in fighting the pandemic. However, significant variations are observed in the willingness to take the vaccination by citizens across different countries. Arguably, differences in vaccination intentions will be influenced by beliefs around vaccines to influence health. Often perceptions of what others are doing and the information available guide individuals' behaviors for vaccination. This is more so in the digital age with the influence of the internet and media. This study aims to determine the factors that impact willingness to vaccinate for COVID-19. We examined factors associated with acceptance of vaccine based on (1) constructs of the Health Belief Model (HBM), (2) sources of information, (3) social media usage, (4) knowledge of COVID-19 treatment, and (5) perception of government's efforts for mitigation. Randomly sampled online survey data was collected by a global firm between December 2020 and January 2021 from 372 citizens (with a response rate of 96.6%) from multiple regions, including North America, the Middle East, Europe, and Asia. Ordered probit regression suggests that the health belief model constructs hold. Perceived severity of COVID-19 (P < 0.001) and action cues of others taking the vaccine positively influences a subject's vaccine intent (P < 0.001), perceived benefits and perceived efficacy of the vaccine positively influences a subject's vaccine intent (P < 0.001). Perceived barriers negatively influence vaccine intent (P < 0.001). Interestingly as for media usage, mainstream media (e.g., TV, newspaper) (P = 0.006) and social media (P = 0.013) both negatively influence a subject's vaccine intent. Social media platforms that are more entertainment and social-based, such as Whatsapp, Instagram, and YouTube, have a negative and significant influence on vaccine intent (P = 0.061), compared to other more information-based social media platforms (e.g., Twitter, LinkedIn). Knowledge of COVID-19 treatment positively influences vaccine intent (P = 0.023). Lastly, governmental efforts' perceived reliability in mitigation strategy (P = 0.028) and response efforts (P = 0.004) negatively influence vaccine intent. The study highlights the "wait-and-see" action cue from others and leaders in the community. It also informs the importance of shaping media information for vaccination through informative media and social media outlets to counteract any misinformation.

Infection in asymptomatic carriers of SARS-CoV-2 can interfere with the achievement of robust immunity on a population scale

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread worldwide as a severe pandemic, and a significant portion of the infected population may remain asymptomatic. Given this, five surveys were carried out between May and September 2020 with a total of 3585 volunteers in the municipality of Foz do Iguaçu, State of Paraná, a triple border region between Brazil/Argentina/Paraguay. Five months after the first infection, volunteers were re-analysed for the production of IgG anti-Spike and anti-RBD-Spike, in addition to analyses of cellular immunity. Seroconversion rates ranged from 4.4 % to a peak of 37.21 % followed by a reduction in seroconversion to 21.1 % in September, indicating that 25 % of the population lost their circulating anti-SARS-CoV-2 antibodies 3 months after infection. Analyses after 5 months of infection showed that only 17.2 % of people still had anti-RBD-Spike antibodies, however, most volunteers had some degree of cellular immune response. The strategy of letting people become naturally infected with SARS-CoV-2 to achieve herd immunity is flawed, and the first contact with the virus may not generate enough immunogenic stimulus to prevent a possible second infection.

Insights into COVID-19 Vaccine Development Based on Immunogenic Structural Proteins of SARS-CoV-2, Host Immune Responses, and Herd Immunity

The first quarter of the 21st century has remarkably been characterized by a multitude of challenges confronting human society as a whole in terms of several outbreaks of infectious viral diseases, such as the 2003 severe acute respiratory syndrome (SARS), China; the 2009 influenza H1N1, Mexico; the 2012 Middle East respiratory syndrome (MERS), Saudi Arabia; and the ongoing coronavirus disease 19 (COVID-19), China. COVID-19, caused by SARS-CoV-2, reportedly broke out in December 2019, Wuhan, the capital of China’s Hubei province, and continues unabated, leading to considerable devastation and death worldwide. The most common target organ of SARS-CoV-2 is the lungs, especially the bronchial and alveolar epithelial cells, culminating in acute respiratory distress syndrome (ARDS) in severe patients. Nevertheless, other tissues and organs are also known to be critically affected following infection, thereby complicating the overall aetiology and prognosis. Excluding H1N1, the SARS-CoV (also referred as SARS-CoV-1), MERS, and SARS-CoV-2 are collectively referred to as coronaviruses, and taxonomically placed under the realm Riboviria, order Nidovirales, suborder Cornidovirineae, family Coronaviridae, subfamily Orthocoronavirinae, genus Betacoronavirus, and subgenus Sarbecovirus. As of 23 September 2021, the ongoing SARS-CoV-2 pandemic has globally resulted in around 229 million and 4.7 million reported infections and deaths, respectively, apart from causing huge psychosomatic debilitation, academic loss, and deep economic recession. Such an unprecedented pandemic has compelled researchers, especially epidemiologists and immunologists, to search for SARS-CoV-2-associated potential immunogenic molecules to develop a vaccine as an immediate prophylactic measure. Amongst multiple structural and non-structural proteins, the homotrimeric spike (S) glycoprotein has been empirically found as the most suitable candidate for vaccine development owing to its immense immunogenic potential, which makes it capable of eliciting both humoral and cell-mediated immune responses. As a consequence, it has become possible to design appropriate, safe, and effective vaccines, apart from related therapeutic agents, to reduce both morbidity and mortality. As of 23 September 2021, four vaccines, namely, Comirnaty, COVID-19 vaccine Janssen, Spikevax, and Vaxzevria, have received the European Medicines Agency’s (EMA) approval, and around thirty are under the phase three clinical trial with emergency authorization by the vaccine-developing country-specific National Regulatory Authority (NRA). In addition, 100–150 vaccines are under various phases of pre-clinical and clinical trials. The mainstay of global vaccination is to introduce herd immunity, which would protect the majority of the population, including immunocompromised individuals, from infection and disease. Here, we primarily discuss category-wise vaccine development, their respective advantages and disadvantages, associated efficiency and potential safety aspects, antigenicity of SARS-CoV-2 structural proteins and immune responses to them along with the emergence of SARS-CoV-2 VOC, and the urgent need of achieving herd immunity to contain the pandemic.

What Happens to the Immune System after Vaccination or Recovery from COVID-19?

Due to its leading role in fighting infections, the human immune system has been the focus of many studies in the context of Coronavirus disease 2019 (COVID-19). In a worldwide effort, the scientific community has transitioned from reporting about the effects of the novel coronavirus on the human body in the early days of the pandemic to exploring the body's many immunopathological and immunoprotecting properties that have improved disease treatment and enabled the development of vaccines. The aim of this review is to explain what happens to the immune system after recovery from COVID-19 and/or vaccination against SARS-CoV-2, the virus that causes the disease. We detail the way in which the immune system responds to a SARS-CoV-2 infection, including innate and adaptive measures. Then, we describe the role of vaccination, the main types of COVID-19 vaccines and how they protect us. Further, we explain the reason why immunity after COVID-19 infection plus a vaccination appears to induce a stronger response compared with virus exposure alone. Additionally, this review reports some correlates of protection from SARS-CoV-2 infection. In conclusion, we reinforce that vaccination is safe and important in achieving herd immunity.