Active surveillance study of adverse events following immunisation of children in the Czech Republic

Danova et al. BMC Public Health (2017) 17:167 DOI 10.1186/s12889-017-4083-4 RESEARCH ARTICLE Open Access Active surveillance study of adverse events following immunisation of children in the Czech Republic Jana Danova* , Aneta Kocourkova and Alexander M. Celko Abstract Background: Despite the undisputed public health benefits of routine vaccination, adverse events following immunisation (AEFI) remain a concern. As most adverse events are mild, they may be under-reported; this may underlie the wide range of AEFI rates reported in the literature. We investigated the rates of AEFI related to routine vaccination of children 0–10 years old in the Czech Republic. Methods: The study reviewed patients’ records in a sample of 49 paediatric GP practices covering all 12 administrative regions of the Czech Republic between 2011 and 2013. Adverse events following routine immunisation of children aged 0–10 years were identified and recorded. Results: The overall rate of AEFI was 209/100,000 doses; this was 6 times higher than the rate reported to the Czech State Institute for Drug Control (34/100,000 doses). Over two fifths (44%) of all AEFI occurred after the booster dose of the combined diphteria, tetanus and pertussis vaccine in 5-year old children. The vast majority of AEFI were non-serious local events (e.g. redness) and fever. Most AEFI occurred the second day after the immunisation, lasted 4 days on average, and were treated by cold therapy, antipyretics and analgesics. Conclusions: The rate of AEFI identified in this study was considerably higher than the officially reported rate. Although the vast majority of AEFI were non-serious, health care providers and the public should be educated and encouraged to report AEFI to address the issue of underreporting, to increase the safety profile of vaccines, and to improve public confidence in immunisation programmes. Keywords: Adverse events following immunisation, Vaccination, Vaccine, Children Background With over 80% of children worldwide immunized, it has been estimated that vaccines save some 2–3,000,000 million deaths each year [1]. In the Czech Republic, with population of 10 million, vaccination prevents about 500 child deaths and some 150,000 non-fatal episodes of infectious diseases annually [2]. Despite these striking public health benefits, a part of the general public continues raising concerns about mass vaccination. The main criticism relates to the potential vaccine-associated risks, including AEFI, although these events are extremely rare and must be weighed against the protective benefits of vaccines [3, 4]. * Correspondence: Department of Epidemiology, Third Faculty of Medicine Charles University, Prague, Czech Republic Adverse events following immunisation can be local (e.g. erythema, oedema, pain) or systemic (e.g. fever, exanthema, allergic reactions), and acute (within minutes of administration) or delayed (several hours or days after administration). Depending on the clinical relevance and severity, AEFI can be classified as physiological and nonphysiological [5, 6]. Physiological adverse events, reflecting natural reaction to the vaccine antigen, are common; they often include elevated body temperature, exanthema and myalgia, and usually have short duration [7–9]. Since physiological reactions are believed to be natural, they are rarely reported. Non-physiological AEFI, sometimes referred to as hyper-reactions, are rare, unexpected and more severe than physiological AEFI, and they tend to occur in immunocompromised patients or patients allergic to vaccine components [10, 11]. The most severe © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Danova et al. BMC Public Health (2017) 17:167 AEFI are either allergic (anaphylaxis) or neurological (encephalopathy, encephalitis, neuritis), and can lead to hospitalization or death [12, 13]. AEFI are identified by either active or passive surveillance [14–16]. Active surveillance often uses electronic system for monitoring of adverse events. Active surveillance will detect more AEFI, but the majority will have milder symptoms [17, 18]. Passive surveillance system relies on voluntary reporting of adverse events sent by physicians and patients [19, 20]; such data are often the basis of administrative reports to national institutions. Passive surveillance system has multiple limitations, including unconfirmed diagnoses, under-reporting of less severe adverse events data, and lack of clarity about the temporal link between AEFI and vaccination and the fact that delayed adverse events are less likely to be reported [21]. In addition, population-based active surveillance allows comparisons of rates of AEFI by vaccination status or by temporal period; this is not possible with passive surveillance. Differences in the methods used to identify AEFI are reflected by the wide range of vaccine-induced adverse events (between 4.8 and 83.0 per 100,000 doses) reported in the literature [3, 8], although the frequency of true allergic AEFI to routine vaccination is estimated be around 1 or 2 per 1,000,000 [7, 17]. Given the uncertainty about the frequency of AEFI, particularly the less severe, it is important to collect data directly from physicians who conduct immunisation and who are the most likely point of first contact when AEFI occur [14, 22]. The aim of the presented study was to investigate the frequency and characteristics of AEFI after routine vaccination of children in the Czech Republic, a country with a long tradition of well organised vaccination system and high immunisation coverage. We actively collected data on AEFI in a sample of paediatrician GPs, and compared the findings with the passive surveillance data reported to the State Institute for Drug Control. In the Czech system of collecting data of AEFI uses only passive reporting system from physicians. Methods We conducted a study of paediatric GP records covering the period 1 January 2011 to 31 December 2013. In the Czech Republic, there are separate GP practices for adults and for children and adolescents (ages 0 to 19 years); these practices provide care for children and adolescents, including vaccination. Vaccines included in the routine compulsory immunisation schedule of children in the Czech Republic are shown in Table 1 [8]. Non-physiologic adverse events following immunisation should be reported to the State Institute for Drug Control and the cau (...truncated)