<h4>Importance</h4>Estimates of the rate of waning of vaccine effectiveness (VE) against COVID-19 are key to assess population levels of protection and future needs for booster doses to face the resurgence of epidemic waves.<h4>Objective</h4>To quantify the progressive waning of VE associated with the Delta and Omicron variants of SARS-CoV-2 by number of received doses.<h4>Data sources</h4>PubMed and Web of Science were searched from the databases' inception to October 19, 2022, as well as reference lists of eligible articles. Preprints were included.<h4>Study selection</h4>Selected studies for this systematic review and meta-analysis were original articles reporting estimates of VE over time against laboratory-confirmed SARS-CoV-2 infection and symptomatic disease.<h4>Data extraction and synthesis</h4>Estimates of VE at different time points from vaccination were retrieved from original studies. A secondary data analysis was performed to project VE at any time from last dose administration, improving the comparability across different studies and between the 2 considered variants. Pooled estimates were obtained from random-effects meta-analysis.<h4>Main outcomes and measures</h4>Outcomes were VE against laboratory-confirmed Omicron or Delta infection and symptomatic disease and half-life and waning rate associated with vaccine-induced protection.<h4>Results</h4>A total of 799 original articles and 149 reviews published in peer-reviewed journals and 35 preprints were identified. Of these, 40 studies were included in the analysis. Pooled estimates of VE of a primary vaccination cycle against laboratory-confirmed Omicron infection and symptomatic disease were both lower than 20% at 6 months from last dose administration. Booster doses restored VE to levels comparable to those acquired soon after the administration of the primary cycle. However, 9 months after booster administration, VE against Omicron was lower than 30% against laboratory-confirmed infection and symptomatic disease. The half-life of VE against symptomatic infection was estimated to be 87 days (95% CI, 67-129 days) for Omicron compared with 316 days (95% CI, 240-470 days) for Delta. Similar waning rates of VE were found for different age segments of the population.<h4>Conclusions and relevance</h4>These findings suggest that the effectiveness of COVID-19 vaccines against laboratory-confirmed Omicron or Delta infection and symptomatic disease rapidly wanes over time after the primary vaccination cycle and booster dose. These results can inform the design of appropriate targets and timing for future vaccination programs.

COVID-19 infection originated in Wuhan, China in December 2019 and crippled human health globally in no time. The public health emergency required urgent efforts to develop and test the efficacy and safety of vaccines to combat the COVID-19 pandemic. The emergency use approval has been granted to COVID-19 vaccines before the completion of conventional phases of clinical trials. However, there is no comprehensive review of safety data reported from the vaccine trials, which is critical information to inform the policies in order to improve uptake of COVID-19 vaccines and mitigate the risk aversion perceived due to the COVID-vaccine side effects. This study aims to systematically review and synthesize the evidence on the safety data from the published COVID-19 vaccine trials. This study followed PRISMA guidelines. We searched three major electronic databases (PubMed, Embase, and Google Scholar) for published studies between Dec 2019 and 2020. Eligible study designs were randomized trials and pre-and post-intervention evaluations. Descriptive findings of included studies were reported stratified by target population, setting, outcomes, and overall results. From PubMed, Embase, WHO database, and Google Scholar screened titles and abstracts, 11 studies were identified in this review. Most of the reactions reported were mild to moderate whereas a few with severe intensity. All reactions resolved within 3-4 days. The commonly reported local adverse events were pain at the site of injection, swelling, and redness. The systemic reactions included fever, fatigue, myalgia, and headache. Some trials also reported laboratory derangements  like decreased hemoglobin, increased bilirubin, altered SGOT and SGPT. None of these alterations were clinically manifested and were self-limiting. Few clinical trials reported serious adverse events, but they were unrelated to vaccination. This systematic review indicates that COVID-19 vaccines can be safe with no serious adverse events. Howev 27 3 2021 36 4 427 427–439 29 3 2021 © Association of Clinical Biochemists of India 2021 Abstract COVID-19 infection originated in Wuhan, China in December 2019 and crippled human health globally in no time. The public health emergency required urgent efforts to develop and test the efficacy and safety of vaccines to combat the COVID-19 pandemic. The emergency use approval has been granted to COVID-19 vaccines before the completion of conventional phases of clinical trials. However, there is no comprehensive review of safety data reported from the vaccine trials, which is critical information to inform the policies in order to improve uptake of COVID-19 vaccines and mitigate the risk aversion perceived due to the COVID-vaccine side effects. This study aims to systematically review and synthesize the evidence on the safety data from the published COVID-19 vaccine trials. This study followed PRISMA guidelines. We searched three major electronic databases (PubMed, Embase, and Google Scholar) for published studies between Dec 2019 and 2020. Eligible study designs were randomized trials and pre-and post-intervention evaluations. None of these alterations were clinically manifested and were self-limiting. Few clinical trials reported serious adverse events, but they were unrelated to vaccination. This systematic review indicates that COVID-19 vaccines can be safe with no serious adverse events. However, long-term post-marketing surveillance data, particularly in high-risk vulnerable populations (elderly and those with co-morbidities, pregnant women, and children) is warranted to ensure the safety of COVID-19 vaccines. Keywords: COVID-19, COVID-19 vaccine, Clinical trials, Adverse effect following immunization, Adverse drug reactions, Vaccination status released display-pdf yes is-olf no is-manuscript no is-preprint no is-journal-matter no is-scanned no is-retracted no Received 2021 Feb 3; Accepted 2021 Mar 3; Issue date 2021 Oct. Introduction The year 2020 will be remembered in modern history as the most challenging year in terms to combat SARS CoV-2, a viral infection causing intense respiratory illness. This pandemic burdened the health professionals globally and led to unprecedented paralysis of health care systems and global economic crisis [ 1 ]. Healthcare practitioners, researchers, and policymakers around the globe were thrown a challenge to deliver adequate prevention and treatment modalities to combat the pandemic. From the initial stage of this pandemic, scientists were focused on either repurposing the existing drugs or developing vaccines against COVID-19 [ 2 ]. The public and private sectors have united together to develop and test the efficacy and safety candidate vaccines. As of January 20th, 2021, one hundred seventy-three The data were synthesized, disagreements were discussed, and differences were resolved between review authors (RK, SD, JC) (Fig. 1 ). Fig. 1 PRISMA flow chart of study selection for systematic review Results We found 196 records using the search term “COVID-19 vaccine trials”. Out of which 52 were full texts of clinical trials assessing the safety of COVID-19 vaccines. After the removal of 14 duplicate studies and articles reporting different primary outcomes ( n = 27), finally, 11 studies were included in this systematic review (Fig. 1 ). As of 21st January 2021, results /interim reports of eleven clinical trials on COVID-19 vaccines were published [ 3 ]. As per the United States Food and Drug Administration guidelines for “Emergency Use Authorization for Vaccines to Prevent COVID-19 Guidance for Industry October 2020, it is recommended that pharmaceutical company must inform the regulatory authority within 24 h of completion of any interim analysis which is intended to be used for attaining Emergency Use Approval (EUA) [ 19 ]. The EUA may be granted based on the interim analysis of clinical endpoint from phase 3 efficacy study and the safety data with a minimum follow-up of two months.

<h4>Introduction</h4>Immunocompromised individuals have been shown to mount a reduced response to vaccination, resulting in reduced vaccine effectiveness in this cohort. Therefore, in the postvaccination era, immunocompromised individuals remain at high risk of breakthrough infection and COVID-19 related hospitalization and death, which persist despite vaccination efforts. There has been a marked paucity of systematic reviews evaluating existing data describing the clinical measures of efficacy of COVID-19 vaccination, specifically in immunocompromised populations. In particular, there is a scarcity of comprehensive evaluations exploring breakthrough infections and severe COVID-19 in this patient population.<h4>Methods</h4>To address this gap, we conducted a systematic review which aimed to provide a summary of current clinical evidence of the effectiveness of COVID-19 vaccination in the immunocompromised population. Using PRISMA guidelines, we conducted a literature search on PubMed and the Cochrane database published between January 1, 2021 to September 1, 2022.<h4>Results</h4>Our findings demonstrated that despite vaccination, immunocompromised patients remained at high risk of new breakthrough COVID-19 infection and severe COVID-19 outcomes compared to the general population. We found increased average relative risk (RR) of breakthrough infections in the immunocompromised population, including patients with cancer (RR = 1.4), HIV (RR = 1.92), chronic kidney disease (RR = 2.26), immunodeficiency (RR = 2.55), and organ transplant recipients (RR = 6.94). These patients are also at greater risk for hospitalizations and death following COVID-19 breakthrough infection. We found that the RR of hospitalization and death in Cancer patients was 1.08 and 2.82, respectively.<h4>Conclusion</h4>This demonstrated that vaccination does not offer an adequate level of protection in these groups, necessitating further measures such as Evusheld and further boosters.

The problem of waning immunity is a major global concern of vaccine programs, with immunity against diseases such as COVID-19 (reduction in efficacy by ~25% in six months), pertussis (waning in 4-12 y), and influenza (annual updates needed) expected to decrease with time. While boosters reduce serious results in high-risk categories, these effects are short-term (4-6 months) and encourage global imbalances, where low-income areas lag in primary vaccination (<2%). Computational models have shown that primary vaccination in underserved regions prevents ~60% of hospitalizations worldwide, surpassing booster-focused measures (~47%). To maintain protection, variant-responsive boosters, rapid booster-design pipelines, universal vaccine platforms (including pan-coronavirus vaccines), and equity-based solutions (decentralized production) need to be integrated. Aligning with frameworks like the Immunization Agenda 2030 of the World Health Organization, plans should balance the expansion of high-risk groups while broadening primary access, providing infrastructure investment, and real-time surveillance to address evolving pathogens and systemic disparities. ABSTRACT The problem of waning immunity is a major global concern of vaccine programs, with immunity against diseases such as COVID-19 (reduction in efficacy by ~25% in six months), pertussis (waning in 4–12 y), and influenza (annual updates needed) expected to decrease with time. While boosters reduce serious results in high-risk categories, these effects are short-term (4–6 months) and encourage global imbalances, where low-income areas lag in primary vaccination (<2%). Computational models have shown that primary vaccination in underserved regions prevents ~60% of hospitalizations worldwide, surpassing booster-focused measures (~47%). 2 With countries shifting away from a non-emergency strategy of combating pandemics to a long-term approach to public health, the necessity to streamline the regimen of vaccination as a booster has gained more and more relevance. Recent research has demonstrated that the efficacy of COVID-19 vaccines in preventing symptomatic SARS-CoV-2 infection may decrease to about 47–69% five months after the initial vaccination, and a faster decrease in the efficacy rate in older and immunocompromised persons. Aging is one of these factors, but an important one, since it restricts the supply of naïve T-cells, causing a rapid decrease in the peaks of antibodies and rapid waning. As an example, post-vaccination, both humoral and cellular immunity are generally weaker in older people, and these effects can be restored by booster doses. 18 Ineffective immune persistence is also affected by immunosuppressive therapies, comorbidities and vaccination schedules. Immunological dissimilarity of systemic and mucosal reactions is a key factor to be considered in vaccine development and efficacy. For example, the live attenuated vaccines like measles induce strong GC memory and long-term humoral memory, a characteristic of many non-replacing vaccines. 20 The immunization against Tetanus toxoid elicits long-term T- and B-cell memory with antibody persistence of multi-years. 21 On the contrary, vaccines against SARS-CoV-2 are mostly directed only against the viral spike protein that undergoes rapid antigen development. New versions exhibit less neutralizing ability of vaccine-induced antibodies, a faster process of apparent functional immune waning in the face of survival of memory B cells. Vaccines Vaccine type Duration of protective immunity Evidence of waning immunity Booster requirement Contributing factors to durability Measles Live-attenuated virus Lifelong in most individuals Minimal waning, rare secondary vaccine failure Not required Long-lived plasma cells, durable memory B and T cells Tetanus Toxoid ≥10 y Gradual decline in antibody titers Every 10 y Antibody-mediated protection Diphtheria Toxoid ~9 y Waning in adolescents Routine Td/Tdap boosters Antibody-mediated protection Pertussis Acellular subunit (aP) 2–3 y Rapid waning and resurgence of disease Adolescent and adult booster required Th2-biased immunity, weak mucosal protection Hepatitis B Recombinant subunit (HBaAg) ≥30–35 y Antibody decline without the loss of immune memory Not required Long-term protection persists despite a gradual decline in B surface antibodies Waning immunity in pertussis and influenza as non-COVID models Two paradigmatic examples of waning vaccine-induced immunity with serious implications for public health include pertussis and influenza. 37 Seasonal influenza vaccines exhibit a different pattern, in which antigenic drift and frequent lineage turnover interact with intrinsic waning to produce short-term protection. Real-world data from recent seasons indicate that vaccine effectiveness against medically attended influenza can decline from initial values in the range of 40–60% to near-null estimates by the end of the season, particularly when circulating strains are antigenically mismatched to the vaccine. 57 AI/ML models have also been applied to multi-omics data from vaccine trials to identify early transcriptional and cellular signatures that predict long-term antibody persistence, enabling the rational adjustment of dose, interval, and adjuvant formulations to favor durable responses. Limitations This is a comprehensive review based on the existing evidence and new strategies for addressing waning immunity, but it has limitations. Available research on both vaccine durability and booster efficacy has different designs, different periods of follow-up, and immunological endpoints, which can impact cross-study comparability. In addition, emerging vaccine platforms and booster approaches with encouraging new preclinical or early clinical results have yet to be validated with regard to long-term safety and scalability and with respect to effectiveness in the real world. These restrictions will not weaken the general findings of this review.

Background: A rise in absenteeism among healthcare workers (HCWs) was recorded during the COVID-19 pandemic, mostly attributed to SARS-CoV-2 infections. However, evidence suggests that COVID-19 vaccine-related side effects may have also contributed to absenteeism during this period. This study aimed to synthesize the evidence on the prevalence of absenteeism related to COVID-19 vaccine side effects among HCWs. Methods: The inclusion criteria for this review were original quantitative studies of any design, written in English, that addressed absenteeism related to the side effects of COVID-19 vaccines among HCWs. Four databases (PubMed, Scopus, Embase, and the Web of Science) were searched for eligible articles on 7 June 2024. The risk of bias was assessed using the Newcastle–Ottawa scale. Narrative synthesis and a meta-analysis were used to synthesize the evidence. Results: Nineteen observational studies with 96,786 participants were included. The pooled prevalence of absenteeism related to COVID-19 vaccine side effects was 17% (95% CI: 13–20%), while 83% (95% CI: 80–87%) of the vaccination events did not lead in any absenteeism. Study design, sex, vaccination dose, region, and vaccine type were identified as significant sources of heterogeneity. Conclusions: A non-negligible proportion of HCWs were absent from work after reporting side effects of the COVID-19 vaccine. Various demographic factors should be considered in future vaccination schedules for HCWs to potentially decrease the burden of absenteeism related to vaccine side effects. As most studies included self-reported questionnaire data, our results may be limited due to a recall bias. Other: The protocol of the study was preregistered in the PROSPERO database (CRD42024552517).

<h4>Background</h4>Human immunodeficiency virus (HIV) and COVID-19 continue to pose significant global public health challenges. Although vaccination is essential for preventing COVID-19 in people with HIV (PWH), evidence on the immunogenicity and safety of booster doses remains limited. This systematic review aimed to assess the immunogenicity and safety of COVID-19 booster vaccination in PWH.<h4>Methods</h4>We conducted a comprehensive literature search in PubMed, EMBASE, and the Cochrane Library. Eligible studies included PWH who had received three or more doses of a COVID-19 vaccine.<h4>Results</h4>Across 54 included studies, 4,685 of 5,229 PWH achieved seroconversion following a third or subsequent COVID-19 vaccine dose-an improvement over rates observed after the primary vaccine series. In 23 studies comparing 2,284 PWH with 1,813 healthy controls (HC), no significant differences in seroconversion rates were found (p ≥ 0.05). Among PWH, 22 studies reported significantly higher seroconversion rates in individuals with CD4⁺ T cell counts >200 cells/mm³ compared to those with counts <200 cells/mm³. Booster vaccination enhanced CD4⁺ T cell responses to levels comparable to HC, although CD8⁺ T cell responses remained markedly lower. Five studies reported adverse events following booster doses, none of which were classified as serious.<h4>Conclusion</h4>COVID-19 booster vaccination is effective in enhancing immune protection and reducing severe disease in PWH. Optimal vaccine dosing is especially important in individuals with low CD4⁺ T cell counts. Tailoring booster strategies may improve seroconversion and overall immune response in this population.<h4>Systematic review registration</h4>https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024605151.

RJPT - Side Effects of Anti-Covid 19 Vaccines in Adults: A Systematic Review You are using an outdated browser. Please upgrade your browser to improve your experience. About Journal Contact Us Research Journal of Pharmacy and Technology ISSN 0974-360X (Online) 0974-3618 (Print) Submit Article Side Effects of Anti-Covid 19 Vaccines in Adults: A Systematic Review Author(s): Latrach Fatima , El Hachemi Ouafae , Ziyyat Abderrahim , Elkhaldi Mohammed , Bouanani Nour El Houda Email(s): nhbouanani@yahoo.fr. *Corresponding Author Published In: Volume - 19 , Issue - 4 , Year - 2026 View HTML Purchase PDF ABSTRACT: Background and Objectives: To respond to the health emergency caused by the Covid-19pandemic, several anti-Covid-19vaccines have been marketed. The speed of their development has prompted several questions about their safety. Therefore, the objective of this study is to carry out a systematic review of the side effects of the anti-Covid 19 vaccines, as well as their associated factors. Material and Methods: The recommendations of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) were used for the selection of the studies included in this review. Articles published in English and French, aiming to identify “the side effects of anti-Covid-19 vaccines in adults” were included. Results: Most of the side effects associated with anti-Covid-19 vaccines are pain at the injection site, fatigue, myalgia and headache. Some rare side effects (myocarditis, thrombocytopenia) are more prevalent with specific types of vaccine (mRNA vaccine and adenoviral vaccine). Other serious adverse events (pulmonary embolism, pericarditis) have been reported but are rare. Conclusion: Anti-Covid 19 vaccines are reasonably safe. Further multicentre studies are needed to identify rare and long-term side effects in order to prevent or better manage them. Keywords: Anti Covid-19 Vaccines Side Effects Safety Meta-analyses. Cite this article: Latrach Fatima, El Hachemi Ouafae, Ziyyat Abderrahim, Elkhaldi Mohammed, Bouanani Nour El Houda. Side Effects of Anti-Covid 19 Vaccines in Adults: A Systematic Review. Research Journal of Pharmacy and Technology. 2026;19(4):1885-5. doi: 10.52711/0974-360X.2026.00271 Cite(Electronic): Latrach Fatima, El Hachemi Ouafae, Ziyyat Abderrahim, Elkhaldi Mohammed, Bouanani Nour El Houda. Side Effects of Anti-Covid 19 Vaccines in Adults: A Systematic Review. Research Journal of Pharmacy and Technology. 2026;19(4):1885-5. Primary Prophylaxis of COVID-19: A Comprehensive Review of approved vaccines. Research Journal of Pharmacy and Technology. 2023; 16(2): 917-3. doi: 10.52711/0974-360X.2023.00154 5. Usha N S,et al. A Study to assess side effects of first dose of Covid-19 Vaccination among GNM students studying at JSS School of Nursing Chamarajanagar. Asian Journal of Nursing Education and Research. 2021; 11(4): 552-4. doi: 10.52711/2349-2996.2021.00129 6. Joseph J, et al. A Descriptive Study to Assess the Knowledge and Attitude towards Covid 19 Vaccination among the Adult Population visitingJubilee Mission Medical College and Research Institute, Thrissur. Sudden sensorineural hearing loss after covid-19 vaccine; A possible adverse reaction? Otolaryngology Case Reports. 2021; 21: 100384. doi:10.1016/j.xocr.2021.100384 40. Shapiro Ben David S, et al. Immediate side effects of Comirnaty COVID-19 vaccine: A nationwide survey of vaccinated people in Israel, December 2020 to March 2021. Eurosurveillance. 2022; 27(13). doi:10.2807/1560-7917.ES.2022.27.13.2100540 41. Riad A, et al. Side Effects of mRNA-Based COVID-19 Vaccines among Young Adults (18–30 Years Old): An Independent Post-Marketing Study. Pharmaceuticals. 2021; 14(10): 1049. doi:10.3390/ph14101049 42. Olivos EN, et al. Reactivity and Safety of BioNTech/Pfizer® Vaccine Anti-SARS-CoV-2, in Health Personnel from the Mexican State of Guanajuato. Biomed Pharmacol J. 2022; 15(2): 993-1003. doi:10.13005/bpj/2435 43. Dabbousi AA, et al. Menstrual abnormalities post-COVID vaccination: a cross-sectional study on adult Lebanese women. Ir J Med Sci. 2023; 192(3): 1163-1170. doi:10.1007/s11845-022-03089-5 44. Visser C, et al. The Immediate Effect of COVID-19 Vaccination on Anticoagulation Control in Patients Using Vitamin K Antagonists. ThrombHaemost. 2022; 122(3): 377-385. doi:10.1055/s-0042-1742628 45. Tanzilli A, et al. Oudjedi A, et al. Reported COVID-19 vaccines side effects among Algerian athletes: a comparison between inactivated virus, adenoviral vector, and mRNA COVID-19 vaccines. The Physician and Sportsmedicine. 2024; 52(2): 134-146. doi:10.1080/00913847.2023.2186691 81. Al-QazazHKh, et al. COVID-19 vaccination, do women suffer from more side effects than men? A

Vaccination prevents millions of fatalities annually and works as one of the most effective and cost-efficient public health interventions. This systematic review critically evaluates vaccine development strategies in the post-COVID-19 era, focusing on platform technologies, delivery systems, and the regulatory and societal challenges that shape vaccine efficacy and accessibility. The COVID-19 pandemic redefined expectations for vaccine science, compressing traditional development timelines, and accelerating the adoption of novel platforms, such as mRNA and viral vectors. While these innovations significantly reduced global morbidity and mortality, they also exposed persistent barriers, including unequal distribution and widespread vaccine hesitancy fuelled by misinformation. This review evaluates the biochemical foundations of vaccine design, including antigen selection, adjuvant use, and delivery optimisation, alongside the emerging formulation strategies and vaccine-platforms integration. The review emphasises the need for continuous alignment between scientific progress and equitable access. By integrating historical context, technical advancement, and social determinants, this review highlights the imperatives for future vaccine strategies to be not only scientifically robust, but also globally inclusive and implementation ready. By positioning recent advancements within the historical timeline of vaccine science, this review argues that the post-COVID-19 era represents an acceleration of progress where speed, adaptability and global equity are essential for safeguarding the populations against current and emerging threats from the pandemics and localized infectious challenges in medical emergencies.