The durability of vaccine-induced protection: an overview.

INTRODUCTION: Current vaccines vary widely in both their efficacy against infection and disease, and the durability of the efficacy. Some vaccines provide practically lifelong protection with a single dose, while others provide only limited protection following annual boosters. What variables make vaccine-induced immune responses last? Can breakthroughs in these factors and technologies help us produce vaccines with better protection and fewer doses? The durability of vaccine-induced protection is now a hot area in vaccinology research, especially after COVID-19 vaccines lost their luster. It has fueled discussion on the eventual utility of existing vaccines to society and bolstered the anti-vaxxer camp. To sustain public trust in vaccines, lasting vaccines must be developed. AREAS COVERED: This review summarizes licensed vaccines' protection. It analyses immunological principles and vaccine and vaccinee parameters that determine longevity of antibodies. The review concludes with challenges and the way forward to improve vaccine durability. EXPERT OPINION: Despite enormous advances, we still lack essential markers and reliable correlates of lasting protection. Most research has focused on humoral immune responses, but we must also focus on innate, mucosal, and cellular responses - their assessment, correlates, determinants, and novel adjuvants. Suitable vaccine designs and platforms for durable immunity must be found.

Conjunctival Involvement in Infants as an Unusual Symptom of Omicron XBB.1.16 Driven Surge.

We describe clinical characteristics of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infected children during the XBB.1.16 variant-driven surge in April, 2023 in India. A signi-ficantly higher positivity rate in young infants than in older children (37.4% vs 13.3%; P<0.001), and a predominance of respiratory symptoms were noticed. Notably, non-purulent con-junctivitis was found in 36.8% of SARS-CoV-2 positive infants. All recovered with symptomatic treatment as outpatients.

Recurring Outbreaks of Circulating Vaccine-derived Polioviruses: Implications for Global Poliovirus Immunization Strategy.

The incidence of polio has decreased by more than 99.9% and currently, only two countries are endemic for wild poliovirus. However, increasing outbreaks of circulating vaccine-derived poliovirus globally in the last few years, with the latest ones in high-income, exclusive inactivated polio virus vaccine (IPV)-using countries have brought out a new dimension to the end game of polio eradication. The inability of the current IPV to induce efficient mucosal immunity in the intestine is likely to be one of the key reasons behind the silent transmission of the polio virus in these countries. New challenges demand concerted global efforts with renewed vigor to cross the last mile. We need to aggressively cover up areas of under-vaccination and continue large-scale genomic surveillance. Further, the availability of a novel oral polio vaccine (nOPV2), and the likely availability of Sabin IPV and a more refined IPV with mucosal adjuvant in the near future is likely to go a long way in achieving this remarkable feat.

Indian Academy of Pediatrics Revised Guidelines on School Reopening: First Revision, September 2021.

JUSTIFICATION: The COVID-19 pandemic has affected schooling for more than 24 crores students, since March 2020. Students need a respite from the long standing social isolation so that they regain their chance to develop holistically, but after the devastating effects of the second wave, the administrators as well as parents are skeptical about the decision of school reopening. PROCESS: The Indian Academy of Pediatrics constituted a task force comprising of national and international experts in the field who deliberated on the issue. OBJECTIVES: To bring out scientifically supported guidelines on the prerequisites of opening and attending the schools, in the current context of the COVID-19 pandemic. RECOMMENDATIONS: The task force recommends i) Decentralization of the school reopening decision; ii)Three epidemiological parameters, case positivity rate (<5 or steadily declining number of cases for past two weeks), number of new cases(<20 per lakh population per day for past two weeks) and vaccination coverage (>60% of the vaccine-eligible population) to be met at the local level, before the schools reopen; and iii) Criteria regarding health and vaccination to be met by the schoolattendees.

Emergency use authorisation of Covid-19 vaccines: An ethical conundrum.

Large-scale vaccination with a safe and effective vaccine against Covid-19 is the only way to conquer the ongoing lethal pandemic that has led to extraordinary social and economic upheaval globally. Fortunately, the world is on the verge of developing Covid-19 vaccines in an unprecedentedly short time. More than forty vaccines are in different stages of clinical trials, and a few are in the crucial phase III studies stage. A new demand for emergency use authorisation and rapid deployment of these vaccines before scrutinising phase III trial data is raging in different quarters. Can advancement of the deployment of these vaccines by even a few weeks give us rich public health dividends? Would it be ethical to deploy these novel vaccines based only on the safety and immunogenicity data generated by the phase-I and II clinical trials? Would it be ethical to deny vaccination of vulnerable populations against an untreatable infectious disease despite the availability of reasonably safe and efficacious vaccines for the want of phase III trial data? The answer is not straightforward, as there are many complexities involved. This commentary attempts to discuss some ethical issues involved in a decision to deploy Covid-19 vaccination before phase III trial results are declared.

Is 'original antigenic sin' complicating indian vaccination drive against Covid-19?

India is in the grip of a devastating second wave of Covid-19. Many experts believe new variants of concern (VOC) are behind this unprecedented surge. Some media reports are hinting toward higher risk of Covid infection following Covid vaccinations. 'Original antigenic sin,' in which a prior exposure to an antigen leads to an ineffective response to a related antigen, may offer one immunological explanation for this unusual association. There is an urgent need of undertaking a detailed study to prove/disprove this association.

Rotavirus Gastroenteritis in Western Uttar Pradesh, India.

OBJECTIVE: To establish hospital-based surveillance to identify cases of rotavirus (RV) among children < 5 y of age hospitalized for acute gastroenteritis (AGE) and to determine the burden and profile of circulating RV genotypes in the region. METHODS: This study was conducted at a tertiary level hospital in Bijnor district of western Uttar Pradesh, India from January 2018 to January 2020. The duly filled case reporting forms and specimens of all the enrolled children were transported in cold chain to the referral laboratory at Christian Medical College (CMC), Vellore on a monthly basis for testing and storage of stool samples as well as data entry and analysis. RESULTS: A total of 1055 under-5 children admitted with AGE, were enrolled. Proper stool specimens were collected from 932 children. Rotavirus was found positive in 368 (39.5%) stool specimens. Marked seasonality was observed in RV-positive cases with the highest incidence was noticed during winter months. The 0-11 mo age group had the highest incidence of RV-GE followed by 12-23 mo. G1 (42.08%) was the most frequent G-type whereas G1P[8] (26.23%) was the commonest circulating genotype. CONCLUSION: The study confirms a significant burden of RV among AGE cases in young children in western Uttar Pradesh. The findings of the study may serve as useful baseline information to the Government of India for assessing vaccine performance after its introduction in the national immunization programmes.

Development of SARS-CoV-2 vaccines: challenges, risks, and the way forward.

The COVID-19 pandemic mandates the development of a safe and effective Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) vaccine. This review analyzes the complexities, challenges, and other vital issues associated with the development of the SARS-CoV-2 vaccine. A brief review of the immune responses (innate, antibody, and T-cell) to SARS-CoV-2, including immune targets, correlates of protection, and duration of immunity is presented. Approaches to vaccine development including different vaccine platforms, critical attributes of novel vaccine candidates, the status of the ongoing clinical trials, and the ways to speed up vaccine development are also reviewed. Despite a historical average success rate of only 6%, and a usual gestation period of 10-12 years for the development of a new vaccine, the world is on the verge of developing COVID-19 vaccines in an extraordinary short time span.

Are BCG-induced non-specific effects adequate to provide protection against COVID-19?

The world is experiencing a pandemic of Coronavirus Disease (COVID-19) caused by type-2 Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). Vaccination is the only option to prevent future surges of the disease. Efforts for developing an effective vaccine are underway, but the timeline for the widespread availability of safe and effective vaccines is unknown. Some ecological reports have linked regional universal use of the Bacillus Calmette-Guerin (BCG) vaccine with reduced morbidity and mortality of COVID-19. BCG protects from non-tuberculous diseases through 'non-specific' effects mediated by the modulation of innate immunity. This commentary provides details of the immunological mechanism of BCG-induced 'trained innate immunity' responsible for its nonspecific protective effects. A probable role of the BCG vaccine in the current pandemic is also examined.

The need & the issues related to new-generation typhoid conjugate vaccines in India.

The low- and middle-income countries bear the highest burden of typhoid fever in the world. India, along with other South Asian countries, has a significant incidence of typhoid fever among young children though there is a paucity of published data on community burden. In spite of the availability of Vi-polysaccharide (Vi-PS) and conjugated Vi-PS vaccines, these are not adequately utilized in India and in the neighbouring countries. To address many shortcomings of the unconjugated Vi-PS vaccines, typhoid conjugate vaccines (TCVs) are developed by conjugating Vi-PS with different carrier proteins. Three such vaccines using tetanus toxoid as a carrier protein are already licensed in India. Several other Vi-PS conjugates are currently in various stages of development. The current review provides an update on the existing and upcoming new TCVs along with a detailed discussion on the various issues involved with their clinical use and limitations.

Adolescent Immunization Schedule: Need for a Relook.

Adolescent immunization is one of the important yet a neglected field in India. There is no adolescent-specific schedule in the government's Universal Immunization Program. Though a separate adolescent immunization schedule exists for the private sector, there is almost no data on the coverage rates of the adolescent vaccines. With the changing epidemiology of certain vaccine preventable diseases, rapid development in the field of vaccinology and the advent of some new vaccines, there is a need to revisit the adolescent vaccination schedule. Common vaccine preventable diseases like dengue, mumps, hepatitis A and typhoid should be given higher priority whereas an alternate strategy should be adopted on the use of the vaccine against diphtheria, tetanus and pertussis.