Adverse Events Following Measles-Mumps-Rubella-Varicella Vaccination and the Case of Seizures: A Post Marketing Active Surveillance in Puglia Italian Region, 2017-2018

A prospective, observational, multi-center, post-marketing safety surveillance study of the GSK combined vaccine against diphtheria, tetanus, pertussis, poliomyelitis, and Haemophilus influenzae type b invasive infections (DTaP-IPV/Hib) in South Korean infants

In South Korea, a combined vaccine against diphtheria, tetanus, pertussis, poliomyelitis, and Haemophilus influenzae type b invasive infections (DTaP-IPV/Hib) is available since 2018 for vaccination of infants from the age of 2 months. This prospective, observational, non-comparative, post-marketing study evaluated the real-world safety of DTaP-IPV/Hib primary vaccination in eligible South Korean infants from the age of 2 months between 2018 and 2022. Infants were followed up for 30 days after each vaccine dose to assess the proportion of infants experiencing any adverse event (AE), including adverse drug reactions (ADRs), unexpected AEs, and serious AEs/serious ADRs (SAEs/SADRs). Of 660 infants vaccinated during the study period, 646 were included in the total safety cohort. A total of 194 AEs were reported in 143 (22.1%) infants; 158 AEs occurred after the first dose in 130 (20.1%) infants, 21 after the second dose in 20 (13.4%) infants, and 11 after the third dose in ten (8.1%) infants. The most frequent AEs by Medical Dictionary for Regulatory Activities Preferred Terms terminology were pyrexia (13.3%), injection site swelling (5.1%), and irritability (1.7%). Most of the AEs were mild, resolved without a medical visit, and were classified as possibly related to vaccination. The incidence proportions of ADRs, unexpected AEs, and SAEs/SADRs were 19.4%, 4.3%, and 0.9%, respectively. All SAEs/SADRs resolved after hospitalization or emergency room visit, and one event was possibly related to vaccination. These results are in line with the approved label and other national/international studies, confirming the acceptable safety profile of DTaP-IPV/Hib in the South Korean pediatric population.

The WHO Algorithm for Causality Assessment of Adverse Effects Following Immunization with Genetic-Based Anti-COVID-19 Vaccines: Pitfalls and Suggestions for Improvement

Clarifying and differentiating the causes of diseases is an essential step in any clinical activity, but it takes on particular relevance and complexity in the case that arise following vaccinations. The WHO has proposed a protocol that uses a list of specific questions about vaccine-related adverse events and an algorithm for making a judgement. Here, we analyze and discuss the important limitations of this protocol when applied to the new genetic-based anti-COVID-19 vaccines, particularly once dealing with rare and unexpected pathological events. The main controversial aspects concern: (a) the prevailing consideration of other possible causes; (b) the biological plausibility and the choice of an appropriate time window to consider adverse effects possibly caused by vaccines; (c) the reference to scientific literature, which may be very limited and often controversial in early stages of introducing new vaccines because of the short period of observation; (d) the final classification of the algorithm into only three classes, which leaves ample space for the "indeterminate" category. Failure to address these issues may lead to distorted pharmacovigilance reports with significant consequences on the benefit/harm assessment. In anticipation of possible future pandemics managed with new vaccines, the WHO algorithm needs to be revised with appropriate protocols for monitoring and evaluation of adverse effects that take into account the novel mechanism of action and real-world epidemiological data.

Active surveillance of immunization adverse effects: a multicentre, open-label, three-arm randomized uncontrolled trial in Ethiopia

BACKGROUND

Participant-centred active adverse event following immunization (AEFI) surveillance can offer real-time vaccine safety data and help in signal detection. This study aimed to evaluate the effectiveness of participant-centred active adverse events (AEs) surveillance following measles immunization in Gedeo Zone health facilities in Ethiopia.

METHODS

An open-label, multicentred, three-arm randomized uncontrolled trial was conducted from 1 June to 21 October 2023. After assessing enrolment eligibility, the study participants were randomized into three groups (short message service [SMS], telephone interview, and diary card). They were expected to report AEs in children 1 week after receiving immunization. Binary and multivariable logistic regression and χ2 tests were used to analyse the data.

RESULTS

Among the 396 participants randomized into the three groups, 80.8% (320 participants) reported back about their children's AE status. Participants in the telephone interview group exhibited a substantially superior response rate (93.2% of 132 participants; p<0.00001) compared with the SMS (71.2%) and diary card (78%) groups. The likelihood of reporting the status of AEs experienced by children was lower by 77% (adjusted odds ratio 0.23 [95% confidence interval 0.1 to 0.52], p-value <0.00001) in the diary card group compared with the telephone interview group.

CONCLUSIONS

In this study, a telephone interview was found to be the best method for AEFI reporting. Participant-centred active AE surveillance could potentially permit more rapid identification of emerging safety signals. Trial registration:  https://clinicaltrials.gov/ct2/show/NCT05803538.

Real-World Effectiveness of the Varicella Vaccine among Children and Adolescents in Qatar: A Case-Control Study

BACKGROUND

Despite the availability of a highly efficacious vaccine, varicella outbreaks are still being reported globally. In this study, we evaluated the real-world effectiveness of varicella vaccination among children between the ages of 1 and 18 years old during the period 2017 to 2019 in Qatar.

METHODS

A matched case-control study was conducted that included all reported varicella-infected children who visited the primary healthcare system in Qatar from January 2017 to December 2019. The cases were children under the age of 18 years who were clinically diagnosed with varicella. The controls were of the same age, who visited the Primary Health Care Corporation (PHCC) during 2017-2019 with a skin rash where varicella infection was ruled out. The data on varicella vaccination for each participant were obtained from the electronic database in the PHCC during the study period.

RESULTS

We included 862 cases of varicella and 5454 matched controls, with a median age of 8 years (IQR 3-12); 47.4% were female and almost 50% were of Qatari nationality. The year 2019 had the highest varicella infection count with a total of 416 cases. The cases were less likely to be vaccinated against varicella, with approximately a quarter (25.6%) of cases and 36.7% of the controls having either one or two doses of the vaccine (p < 0.001). Compared to not being vaccinated, a single dose vaccination showed a 56% reduction in the odds of varicella infection [OR 0.44, 95% CI: 0.34-0.55; p < 0.000], and a two-dose vaccination showed an 86% reduction in the odds of varicella infection [OR 0.13, 95% CI: 0.06-0.29; p < 0.000].

CONCLUSION

In this multicultural setting, a two-dose varicella vaccination shows reasonable protection against varicella infection.

Allergic adverse events following immunization: Data from post-marketing surveillance in Apulia region (South of Italy)

Introduction

Among adverse events following immunization (AEFIs), allergic reactions elicit the most concern, as they are often unpredictable and can be life-threatening. Their estimates range from one in 1,000,000 to one in 50,000 vaccine doses. This report describes allergic events following immunization reported from 2020 to 2021 in Puglia, a region in the South-East of Italy with around 4 million inhabitants. Its main objective is to describe the allergic safety profile of currently employed vaccines.

Materials and methods

This is a retrospective observational study. The study period spanned from January 2020 to December 2021, and the whole Apulian population was included in the study. Information regarding AEFIs reported in Puglia during the study period was gathered from the Italian Drug Authority's pharmacovigilance database (National Pharmacovigilance Network, RNF). The overall number of vaccine doses administered was extrapolated by the Apulian online immunization database (GIAVA). Reporting rates were calculated as AEFIs reported during a certain time span/number of vaccine doses administered during the same period.

Results

10,834,913 vaccine doses were administered during the study period and 95 reports of allergic AEFIs were submitted to the RNF (reporting rate 0.88/100,000 doses). 27.4% of the reported events (26/95) were classified as serious (reporting rate 0.24/100,000 doses). 68 out of 95 (71.6%) adverse events were at least partially resolved by the time of reporting and none of them resulted in the subject's death.

Conclusions

Allergic reactions following vaccination were rare events, thus confirming the favourable risks/benefits ratio for currently marketed vaccines.

Combined measles-mumps-rubella-varicella vaccine and febrile convulsions: the risk considered in the broad context

INTRODUCTION

Studies on quadrivalent measles, mumps, rubella, and varicella (MMRV) vaccines have indicated a twofold increased relative risk of febrile convulsion (FC) after the first dose compared to MMR and V administered at the same medical visit (MMR+V).

AREAS COVERED

This narrative review contextualizes FC occurrence after the first MMRV vaccine dose from a clinical perspective and outlines approaches to attenuate FC occurrence post-vaccination.

EXPERT OPINION

While the relative FC risk increases after the first dose of MMRV compared to MMR+V vaccine in measles-naïve infants, the attributable risk is low versus the overall FC risk in the pediatric population triggered by other causes, like natural exposure to pathogens or routine vaccination. No increased risk of FC has been reported after MMRV co-administration with other routine vaccines compared to MMRV alone. Based on our findings and considering the MMRV vaccination benefits (fewer injections, higher coverage, better vaccination compliance), the overall benefit-risk profile of MMRV vaccine is considered to remain positive. Potential occurrence of FC in predisposed children (e.g. with personal/family history of FC) may be attenuated if they receive MMR+V instead of MMRV as the first dose. It is also important to monitor vaccinees for fever during the first 2 weeks post-vaccination.

Safety profile of MenB-FHBp vaccine among adolescents: data from surveillance of Adverse Events Following Immunization in Puglia (Italy), 2018-2020

MenB-FHBp was licensed in Europe in 2017 from the age of 10. In the “postmarketing life” of a new vaccine, surveillance of Adverse Events Following Immunization (AEFI) is crucial, to better understand the pattern of safety and the effectiveness. This paper describes the MenB-FHBp AEFIs notified in Puglia in 2018–2021, to take a picture of the safety profile of this vaccine in the real life, four years after its introduction in Italy. This is a retrospective observational study. Data were collected from the list of AEFIs notified after MenB-FHBp vaccine administration in Puglia in 2018–2020, and the number of doses of this vaccine administered in the same period. AEFIs were classified according to WHOʻs algorithm, and causality assessment was carried out for serious AEFIs. From January 2018 to December 2020, in Puglia, 43,061 doses of MenB-FHBp were administered and 42 MenB-FHBp AEFIs (reporting rate: 97.5 per 100,000 doses administered) were reported. Among these, 12 were classified as severe (28.6%; reporting rate 27.9 per 100,000 doses). Overall, the male/female ratio in AEFIs was 1:1. The median age of people who suffered from AEFIs was 12 years (range 11–13). For the 11 serious AEFIs for which the classification was “consistent causal association,” the diagnosis was hyperpyrexia (reporting rate 13.9 per 100,000 doses), fainting (rate 4.6 per 100,000 doses), urticaria (rate 2,3 per 100,000 doses), convulsions (rate 2,3 per 100,000 doses), and vomit (rate 2,3 per 100,000 doses). No deaths or impairment were notified in studied AEFIs. The picture of MenB-FHBp vaccine supports that the risk of AEFIs is in line with previous published data and in general acceptable.

Comparison of varicella outbreaks in schools in China during different vaccination periods

The purpose of this study was to investigate the outbreak trend of chickenpox and the epidemiological characteristics of outbreak related cases from 2017 to 2021, and compare the impact of voluntary self-funded single dose vaccination versus mandatory two-dose vaccine vaccination on varicella outbreaks. The data of varicella outbreaks in Jiangsu Province from 2017 to 2021 come from the national public health emergency management information system. We randomly chose 70 outbreaks from 2019 to 2020 for study in order to better understand the features and regularity of breakthrough varicella(BV). In pilot cities with two doses of free VarV, the number of outbreaks decreased from 306 in 2017 to 123 in 2021, while the total number of cases related to the outbreak decreased by 64.6% (P < .01), the median size of the outbreak decreased from 24 cases (range:6-146) to 21 cases (range:10-93) (P < .01), and the incidence rate also decreased from 2.01/100 to 1.33/100. The proportion of cases with high fever, severe rash and complications in the BV group was lower than that in the primary varicella (PV), and the differences were statistically significant. The incidence rate of varicella among students who had post-exposure prophylaxis (PEP) activities was 1.42% (488/ 33,878), and 1.63% (2468/ 148,943) among those who did not (p = .005). The single-dose varicella vaccination was less effective in controlling the outbreaks, and the success of the full implementation of the routine two-dose varicella vaccination plan in the pilot cities provided a basis for implementation in the whole province, and long-term follow-up studies are needed to evaluate the effect of the new strategy in the future.

Sex and age as determinants of the seroprevalence of anti-measles IgG among European healthcare workers: A systematic review and meta-analysis

INTRODUCTION

The international literature shows good evidence of a significant rate of measles susceptibility among healthcare workers (HCWs). As such, they are an important public health issue.

METHODS

We conducted a systematic review and meta-analysis to estimate the prevalence of susceptible HCWs in EU/EEA countries and in the UK and to explore the characteristics (sex and age differences) and management of those found to be susceptible.

RESULTS

Nineteen studies were included in the meta-analysis. The prevalence of measles-susceptible HCWs was 13.3% (95 %CI: 10.0-17.0%). In a comparison of serosusceptible female vs. male HCWs, the RR was 0.92 (95 %CI = 0.83-1.03), and in a comparison of age classes (born after vs. before 1980) the RR was 2.78 (95 %CI = 2.20-3.50). The most recent studies proposed the mandatory vaccination of HCWs.

DISCUSSION

According to our meta-analysis, the prevalence of serosusceptible European HCWs is 13%; HCWs born in the post-vaccination era seem to be at higher risk. Healthcare professionals susceptible to measles are a serious epidemiological concern. Greater efforts should therefore be made to identify those who have yet to be vaccinated and actively encourage their vaccination.

Immediate side effects of Comirnaty COVID-19 vaccine: A nationwide survey of vaccinated people in Israel, December 2020 to March 2021

BackgroundCOVID-19 vaccine safety is of major interest worldwide, since there is no prior experience with it. Israel was one of the first countries to widely use the Comirnaty vaccine.AimWe aimed to assess the vaccine's short-term side effects directly from a large population and to predict influencing factors for self-reporting side effects.MethodsIn a retrospective cohort study, we investigated self-reported systemic vaccine side-effects using electronic surveys sent to vaccinated individuals between 20 December 2020 and 11 March 2021, within 3 days following administration of the first and second dose. We determined predictors for reporting systemic side effects by logistic regression.ResultsA total of 1,213,693 patients received at least one vaccine dose and 301,537 (24.8%) answered at least one survey. Among them, 68,162 (30.4%) and 89,854 (59.9%) individuals filled the first and the second dose surveys, respectively, and reported one or more side effects. Most common side effects were fatigue, headache and myalgia. Several respondents reported facial paraesthesia after first and second dose, respectively (n = 1,675; 0.7% and n = 1,601; 1.1%). Individuals younger than 40 years and women reported side effects more frequently than others, but pregnant women reported less. Pregnancy was a weak predictor for reporting any side effect in general and in particular fatigue, myalgia, headache, chills and fever.ConclusionsWe found further support for minor short-term side effects, within 3 days of receiving the Comirnaty vaccine. These findings from vaccine recipients in general and pregnant women in particular can improve vaccine acceptance.

Public Health Surveillance for Adverse Events Following COVID-19 Vaccination in Africa

Local, national, and international health agencies have advocated multi-pronged public health strategies to limit infections and prevent deaths. The availability of safe and effective vaccines is critical in the control of a pandemic. Several adverse events have been reported globally following reception of different vaccines, with limited or no data from Africa. This cross-sectional epidemiological study investigated adverse events following COVID-19 vaccination in Africans from April-June, 2021 using a structured online questionnaire. Out of 1200 participants recruited, a total of 80.8% (n = 969) respondents from 35 countries, including 22 African countries and 13 countries where Africans live in the diaspora, reported adverse events. Over half of the vaccinees were male (53.0%) and frontline healthcare workers (55.7%), respectively. A total of 15.6% (n = 151) reported previous exposure to SARS-CoV-2, while about one-fourth, 24.8% (n = 240), reported different underlying health conditions prior to vaccination. Fatal cases were 5.1% (n = 49), while other significant heterogenous events were reported in three categories: very common, common, and uncommon, with the latter including enlarged lymph nodes 2.4% (n = 23), menstrual disorder 0.5% (n = 5), and increased libido 0.2% (n = 2). The study provided useful data for concerned authorities and institutions to prepare plans that will address issues related to COVID-19 vaccines.

Real-Life Safety Profile of the 9-Valent HPV Vaccine Based on Data from the Puglia Region of Southern Italy

Human Papillomavirus (HPV) is responsible for epithelial lesions and cancers in both males and females. The latest licensed HPV vaccine is Gardasil-9®, a 9-valent HPV vaccine which is effective not only against the high-risk HPV types, but also against the ones responsible for non-cancerous lesions. This report describes adverse events following Gardasil-9® administration reported in Puglia, southern Italy, from January 2018 to November 2021. This is a retrospective observational study. Data about the adverse events following immunization (AEFIs) with Gardasil-9® were collected from the Italian Drug Authority database. AEFIs were classified as serious or non-serious accordingly to World Health Organization guidelines, and serious ones underwent causality assessment. During the study period, 266,647 doses of 9vHPVv were administered in Puglia and 22 AEFIs were reported, with a reporting rate (RR) of 8.25 per 100,000 doses. The most reported symptoms were neurological ones (7/22). A total of 5 (22.7%) AEFIs were classified as serious, and 2 of these led to the patient's hospitalization. In one case, permanent impairment occurred. Following causality assessment, only 2 out of 5 serious AEFIs were deemed to be consistently associated with the vaccination (RR: 0.750 per 100,000 doses). The data gathered in our study are similar to the pre-licensure evidence as far as the nature of the AEFIs is concerned. The reporting rate, though, is far lower than the ones described in clinical trials, likely due to the different approach to data collection: in our study, data were gathered via passive surveillance, while pre-marketing studies generally employ active calls for this purpose. Gardasil-9®'s safety profile appears to be favorable, with a low rate of serious adverse events and a risk/benefits ratio pending for the latter.

Attitude for vaccination prophylaxis among pregnant women: a cross-sectional study

Pregnant women and newborns are considered a subgroup of population at increased risk for several infectious diseases, some of which are vaccine-preventable. Anti-diphtheria-tetanus-pertussis vaccine (dTpa) and influenza vaccine are recommended for pregnant women. We carried out a study to evaluate the knowledge of new mothers toward the main vaccine-preventable diseases and to assess their compliance with recommended vaccinations. Using the Hospital Discharge Forms (SDO), the list of women who gave birth in 2018 was generated. Women were interviewed by a questionnaire administered by telephone. The study sample consisted of 145 subjects, with an average age of 35.0 ± 5.9 years (range = 18.0–47.0). 5/145 (3.4%; 95% CI = 1.1–7.9%) subjects were advised during pregnancy to have the flu shot; only 1/145 (0.7%; 95% CI = 0.5–71.6%) reported the flu vaccine during the last pregnancy. 94/145 (64.8%; 95% CI = 57.2–73.2%) respondents declared that they had carried out the TORCH panel exams before pregnancy; of these 18/94 (19.2%; 95% C = 11.8–28.6%) were susceptible for rubella. Of these subjects, for 7/18 (38.9%; 95% CI = 17.3–64.3%) rubella vaccination was offered and 5/7 (71.4%; 95% CI = 29.0–96.3%) decided to carry out the vaccination. Only 1/145 (0.7%; 95% CI = 0.0–3.8%) of the interviewed woman underwent anti-dTap vaccination. Greater efforts must be made by public health institutions to raise awareness and improve vaccination compliance in this population.

Safety Profile of Recommended Vaccinations in Adolescents: Data from Surveillance of Adverse Events Following Immunization in Puglia (Italy), 2016-2020

Adolescence is a critical period for immunization, in which the adhesion rate to recommended vaccinations is often lower than desired. Since the safety of new vaccines is one of the most important factors determining vaccination hesitancy, post-marketing surveillance of adverse events following immunization (AEFIs) is recommended by the World Health Organization (WHO) to better understand the safety of these drugs. This report describes AEFIs notified in Puglia (Italy) after recommended vaccinations in adolescents aged 12 to 18 years in 2016–2020 to determine the safety profile of these products in a real-life scenario. This is a retrospective observational study. Data were gathered from the list of AEFIs notified in subjects between 12 and 18 years of age following administration of recommended vaccines in Puglia in 2016–2020. AEFIs were classified according to the WHO’s decisional algorithm, and causality assessment was carried out for serious AEFIs. From 2016 to 2020, 323,627 doses of vaccine were administered to adolescents in Puglia and 50 AEFIs were reported (reporting rate: 15.4 × 100,000 doses). Of these, 17 (34.0%) were classified as serious, and causality assessment identified 13 of them (76.5%) as vaccine related. The most common symptoms were local reactions, fever and neurological symptoms. No deaths were notified. The benefits of immunization in adolescents appear to be greater than the risk of AEFIs for all studied vaccines; in fact, AEFIs occur in less than 0.1‰ of patients and are generally mild and self-limiting.

Two years of on-site influenza vaccination strategy in an Italian university hospital: main results and lessons learned

Although the vaccination of healthcare workers (HCWs) is considered essential for preventing influenza circulation in the hospital setting, vaccination coverage (VC) in this group remains low. Among the reasons cited by HCWs is a lack of time to attend the vaccination clinic. For the 2018/2019 influenza season, active (on-site) influenza vaccination was offered directly in 44 operative units (OUs) of the Bari Policlinico hospital (50 OUs, 3,397 HCWs). At the same time, the hospital granted the HCW access to the vaccination clinic during October and December 2018. VC achieved among HCWs of Bari Policlinico during the 2018/2019 influenza season was then analyzed, and the results compared with those of the 2017/18 season. During the 2018/19 season, VC was 20.4% (n = 798) and thus higher than the 14.2% of the 2017/18 season (+6.2%). The highest VC was among physicians (33.4%), followed by other HCWs (23.8%), auxiliary staff (8.6%), and nurses (7.2%). Overall, 284 (36.5%) HCWs were vaccinated at on-site sessions. Multivariate analysis showed that vaccination uptake was associated with male gender and with work in OU where vaccination was actively offered. On the other hand, being a nurse or auxiliary staff member and working in the surgical area were deterrents. Although VC remained unsatisfactory, active on-site vaccination proved to be an important strategy to improve vaccination compliance, increasing 44% compared to the previous season. Nonetheless, mandatory vaccination directed by public health institutions may be the only way to reach a minimum level of coverage.

Long-term immunogenicity after measles vaccine vs. wild infection: an Italian retrospective cohort study

The persistence of specific IgG after measles infection and after measles vaccination has not been sufficiently investigated. Current evidence suggests that immunity after the disease is life-long, whereas the response after two doses of measles-containing vaccine declines within 10-15 years. This study evaluated the proportion of individuals with detectable anti-measles IgG in two groups, those vaccinated with two doses of anti-MMR vaccine and those with a self-reported history of measles infection. Among the 611 students and residents who were tested, 94 (15%) had no detectable protective anti-measles IgG. This proportion was higher among vaccinated individuals (20%; GMT = 92.2) than among those with a self-reported history of measles (6%; GMT = 213.3; p < .0001). After one or two MMR vaccine booster doses, the overall seroconversion rate was 92%. An important proportion of people immunized for measles did not have a protective IgG titer in the years after vaccination, but among those who had a natural infection the rate was three-fold lower. This finding should be considered in the pre-elimination phase, given the resurgence of measles cases among individuals who after being vaccinated lost their circulating IgG after several years, especially if they failed to receive a natural booster.

Long -term persistence of antibodies against varicella in fully immunized healthcare workers: an Italian retrospective cohort study

Background

Chickenpox is a highly contagious disease caused by the varicella zoster virus (VZV), and in infants, adolescents, adults, pregnant women, and the immunocompromised it can be serious. The best way to prevent chickenpox is immunization with the varicella vaccine. Protective levels of antibodies induced by the varicella vaccine decline over time, but there is currently no formal recommendation for testing anti-varicella zoster virus (VZV) IgG levels in immunized healthcare workers (HCWs).

Methods

The aims of this study were to evaluate the seroprevalence of circulating anti-VZV IgG in a sample a sample of students and residents of the medical school of the University of Bari, the long-term immunogenicity of the varicella vaccine, and the effectiveness of a strategy consisting of a third vaccine booster dose. The study population was screened as part of a biological risk assessment conducted between April 2014 and October 2020. A strategy for the management of non-responders was also examined.

Results

The 182 students and residents included in the study had a documented history of immunization (two doses of varicella vaccine). The absence of anti-VZV IgG was determined in 34% (62/182; 95%CI = 27.2–41.4%), with serosusceptibility more common among males than females (p < 0.05). After a third varicella dose, seroconversion was achieved in 100% of this previously seronegative group. No serious adverse events were recorded.

Conclusions

One-third of the study population immunized against VZV lacked a protective antibody titer, but a third dose of vaccine restored protection. Since it is highly unlikely that VZV will be eliminated in the immediate future, the loss of immunity in a substantial portion of the population implies a risk of varicella outbreaks in the coming years. Screening for varicella immunity in routine assessments of the biological risk of medical students and HCWs may help to prevent nosocomial VZV infections.

Post-Marketing Active Surveillance of Adverse Reactions Following Influenza Cell-Based Quadrivalent Vaccine: An Italian Prospective Observational Study

Since the influenza season 2018/19, the Italian Ministry of Health recommended a dose of cell-based quadrivalent vaccine (Flucelvax Tetra) for HCWs (healthcare workers), because this vaccine seemed more efficacious in the prevention of AH3N2 virus. Due to the lack of pre-registration data, the safety profile of this new vaccine must be investigated in post-marketing surveillance. The aim of our study is to evaluate, through a post-marketing active surveillance program developed during the 2019/20 influenza season, any Adverse Events Following Immunization (AEFIs) that happened in the 7 days after immunization with Flucelvax Tetra. The study was carried out in a sample of HCWs of Policlinico General University-Hospital (Apulia, South Italy). AEFIs were classified as ‘serious’ or ‘not serious’ according to the WHO (World Health Organization) guidelines; the WHO causality assessment algorithm was applied to classify serious AEFIs. A total of 741 HCWs were enrolled, and 430 AEFIs (reporting rate: 58.0 (95%CI: 54.4–61.6) × 100 enrolled) were recorded. Of these, 429 of 430 (99.8%; reporting rate: 57.8 (95%CI: 54.2–61.5) × 100 enrolled) were classified as not serious and one (0.2%; reporting rate: 0.13 (0.03–0.75) × 100 enrolled) was classified as serious. Local reactions were the adverse reaction reported most frequently (88%); regarding the serious AEFI, causality assessment excluded the causal link with the administration of the vaccine. All the AEFIs resolved without sequelae. Flucelvax Tetra showed a profile of high safety. Due to their characteristics of greater sensitivity than passive surveillance, active surveillance programs can be useful in defining the safety profiles of a given vaccine/drug in certain population subgroups.

Adverse events following measles-mumps-rubella-varicella vaccine: an independent perspective on Italian pharmacovigilance data

Vaccine surveillance programs are crucial for the analysis of the vaccine’s safety profile and the guidance of health policies. The Epidemiological Observatory of the Italian Apulia Region carried out an active surveillance program of adverse effects following immunization (AEFI) after the first dose of the measles-mumps-rubella-varicella (MMRV) vaccine, finding 462 AEFIs per 1000 doses, with 11% rated serious. Applying the World Health Organization (WHO) causality assessment algorithm, 38 serious AEFIs/1000 enrolled were classified as ‘consistent causal associations’ with MMRV immunization. Severe hyperpyrexia, neurological symptoms and gastrointestinal diseases occurred in 38, 20 and 15 cases/1000 enrolled, respectively. A projection of such AEFIs in an Italian birth cohort would give tens of thousands of serious AEFIs. These incidence data are much greater than the incidence of serious AEFIs reported by the Italian Medicines Agency (AIFA) for years 2017 and 2018, mainly based on passive (or mixed) pharmacovigilance. In a previous epidemiological study in the same Italian Region, during an eight year passive surveillance, the reporting rate of serious AEFI was 0.06/1000 doses, and no cases of febrile seizures were detected applying the WHO algorithm. Taken together, the data suggest that passive pharmacovigilance is utterly inadequate to document the real incidence of serious AEFIs and that current methods of assessing causality may be questioned. Active surveillance programs are required in representative population samples, with results presented separately from those of spontaneous reporting, and causality assessment should be performed carefully and using a correct technique for AEFIs presenting as complex and multifactorial diseases, like those with serious neurologic disorders.

Vaccines

In this volume of the Side Effects of Drugs Annual, although other vaccines will be covered, the safety of COVID vaccines is the focus as COVID-19 has led to heightened attention on vaccine safety in general. As such, this chapter will be more relevant than ever before. As noted in past SEDA issues, clinicians should be mindful of the risks of AEs and SAEs associated with each vaccine.

Adverse events following measles-mumps-rubella-varicella vaccine: an independent perspective on Italian pharmacovigilance data

Vaccine surveillance programs are crucial for the analysis of the vaccine’s safety profile and the guidance of health policies. The Epidemiological Observatory of the Italian Apulia Region carried out an active surveillance program of adverse effects following immunization (AEFI) after the first dose of the measles-mumps-rubella-varicella (MMRV) vaccine, finding 462 AEFIs per 1000 doses, with 11% rated serious. Applying the World Health Organization (WHO) causality assessment algorithm, 38 serious AEFIs/1000 enrolled were classified as ‘consistent causal associations’ with MMRV immunization. Severe hyperpyrexia, neurological symptoms and gastrointestinal diseases occurred in 38, 20 and 15 cases/1000 enrolled, respectively. A projection of such AEFIs in an Italian birth cohort would give tens of thousands of serious AEFIs. These incidence data are much greater than the incidence of serious AEFIs reported by the Italian Medicines Agency (AIFA) for years 2017 and 2018, mainly based on passive (or mixed) pharmacovigilance. In a previous epidemiological study in the same Italian Region, during an eight year passive surveillance, the reporting rate of serious AEFI was 0.06/1000 doses, and no cases of febrile seizures were detected applying the WHO algorithm. Taken together, the data suggest that passive pharmacovigilance is utterly inadequate to document the real incidence of serious AEFIs and that current methods of assessing causality may be questioned. Active surveillance programs are required in representative population samples, with results presented separately from those of spontaneous reporting, and causality assessment should be performed carefully and using a correct technique for AEFIs presenting as complex and multifactorial diseases, like those with serious neurologic disorders.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to national vaccine injury compensation programs. If manufacturing defects or vaccine storage and delivering errors are excluded, the majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that can explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents some concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to vaccine injury compensation programs. The majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that might explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents several concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. Given these inadequacies in the evaluation of multifactorial diseases, the WHO guidelines need to be reevaluated and revised. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.