Allergic adverse events following 2015 seasonal influenza vaccine, Victoria, Australia

Vaccine adverse event mentions in social media: Mining the language of Twitter conversations (Preprint)

Background

Traditional monitoring for adverse events following immunization (AEFI) relies on various established reporting systems, where there is inevitable lag between an AEFI occurring and its potential reporting and subsequent processing of reports. AEFI safety signal detection strives to detect AEFI as early as possible, ideally close to real time. Monitoring social media data holds promise as a resource for this.

Objective

The primary aim of this study is to investigate the utility of monitoring social media for gaining early insights into vaccine safety issues, by extracting vaccine adverse event mentions (VAEMs) from Twitter, using natural language processing techniques. The secondary aims are to document the natural language processing techniques used and identify the most effective of them for identifying tweets that contain VAEM, with a view to define an approach that might be applicable to other similar social media surveillance tasks.

Methods

A VAEM-Mine method was developed that combines topic modeling with classification techniques to extract maximal VAEM posts from a vaccine-related Twitter stream, with high degree of confidence. The approach does not require a targeted search for specific vaccine reaction–indicative words, but instead, identifies VAEM posts according to their language structure.

Results

The VAEM-Mine method isolated 8992 VAEMs from 811,010 vaccine-related Twitter posts and achieved an F₁ score of 0.91 in the classification phase.

Conclusions

Social media can assist with the detection of vaccine safety signals as a valuable complementary source for monitoring mentions of vaccine adverse events. A social media–based VAEM data stream can be assessed for changes to detect possible emerging vaccine safety signals, helping to address the well-recognized limitations of passive reporting systems, including lack of timeliness and underreporting.

Post-vaccination healthcare attendance rate as a proxy measure for syndromic surveillance of adverse events following immunisation

OBJECTIVE

This study explored whether all-cause healthcare attendance rate post-vaccination could detect the two historical influenza safety episodes occurring in 2010 and 2015 using a large de-identified general practitioner (GP) consultations dataset.

METHODS

A retrospective observational cohort study was conducted using GP consultation data routinely collected from 2008 to 2017 in Victoria, Australia. Post-vaccination GP consultation rates were monitored, over a 22-week surveillance period each year that aligned with each year's influenza vaccination season, using the Observed minus Expected (O-E) and the Log-Likelihood Ratio (LLR) CUSUM charts. Days 1-7 post-vaccination were considered as the risk period. The LLR CUSUM was designed to detect both a 50% and two-fold rise in the odds of the baseline post-vaccination GP consultation rates.

RESULTS

Over the 10-year study period, more than 1.5 million seasonal influenza vaccines doses were administered to 295,091 persons. Overall, 1.29% had a GP consultation within one week of vaccination, but 98.53% of the consultations occurred in days 1-3 post-vaccination. The LLR CUSUM chart detected significant increases in the weekly rates of post-vaccination GP consultation in 2010 in children aged under ten years and in 2015 in adults aged 19-64 years. These increases were aligned by week, but one week earlier and by age category, with the historical adverse events following immunisation (AEFI) signals occurring in 2010 and 2015. However, in the absence of historical AEFI signals, increased rates of post-vaccination GP consultations were identified in three of the eight influenza vaccination years.

CONCLUSION

The crude post-vaccination healthcare attendance rate has the potential to offer a sensitive proxy to monitor vaccine safety signal. Implications for public health: Vaccine safety monitoring using syndromic indicator has the potential to augment the existing surveillance systems as part of an integrated vaccine safety monitoring approach.

Early signal detection of adverse events following influenza vaccination using proportional reporting ratio, Victoria, Australia

INTRODUCTION

Timely adverse event following immunisation (AEFI) signal event detection is essential to minimise further vaccinees receiving unsafe vaccines. We explored the proportional reporting ratio (PRR) ability to detect two known signal events with influenza vaccines with the aim of providing a model for prospective routine signal detection and improving vaccine safety surveillance in Australia.

METHODS

Passive AEFI surveillance reports from 2008-2017 relating to influenza vaccines were accessed from the Australian SAEFVIC (Victoria) database. Proportional reporting ratios were calculated for two vaccine-event categories; fever and allergic AEFI. Signal detection sensitivity for two known signal events were determined using weekly data; cumulative data by individual year and; cumulative for all previous years. Signal event thresholds of PRR ≥2 and Chi-square ≥4 were applied.

RESULTS

PRR provided sensitive signal detection when calculated cumulatively by individual year or by all previous years. Known signal events were detected 15 and 11 days earlier than traditional methods used at the time of the actual events.

CONCLUSION

Utilising a single jurisdiction's data, PRR improved vaccine pharmacovigilance and showed the potential to detect important safety signals much earlier than previously. It has potential to maximise immunisation safety in Australia. This study progresses the necessary work to establish national cohesion for passive surveillance signal detection and strengthen routine Australian vaccine pharmacovigilance.

Challenges in implementing yearly enhanced safety surveillance of influenza vaccination in Europe: lessons learned and future perspectives

Seasonal influenza vaccines are frequently reformulated, leading to specific challenges for continuous benefit/risk monitoring. In 2014, the European Medicines Agency started requiring annual enhanced safety surveillance (ESS). This article provides a perspective on ESS studies conducted ever since and aims to map existing initiatives used to monitor adverse events following influenza immunization. Of 11 ESS studies, reporting surveillance data of at least five different vaccine brands during four seasons, all were able to rapidly capture vaccine-specific adverse events of interest reports. However, challenges have been identified during study implementation, including recruitment of sufficient participants, enrolling younger age groups, collecting data of vaccine batch numbers, comparing observed with expected rates and achieving adequate return of reported events. Harmonizing safety monitoring standards across countries, and bridging between routine pharmacovigilance and ESS, is likely to allow more comprehensive assessments of influenza vaccine safety, requiring close collaboration between regulators, public health, and manufacturers.

Rapid assessment of enhanced safety surveillance for influenza vaccine

OBJECTIVES

The enhanced safety surveillance for seasonal influenza vaccines established by the European Medicines Agency is required each season. Therefore, a registry capable of rapidly detecting and evaluating potential new safety concerns is needed. The aim of the study is to demonstrate the effectiveness of the vaccine information system of the Valencia region to make a rapid assessment of the influenza vaccine safety and describe the safety of the two vaccine types used in the 2017/2018 season.

STUDY DESIGN

It is a population-based descriptive study.

METHODS

Adverse events following immunization reports collected from 23rd October 2017 to 15th March 2018 were analyzed.

RESULTS

A total of 55 adverse events for influenza vaccine were reported in season 2017/2018 with a reporting rate (RR) of 0.77 per 10,000 administered doses. Injection site reactions had a RR of 0.30 and 0.47 per 10,000 for subunit and adjuvanted vaccines, respectively. Differences per vaccine, sex, and risk group did not reach statistical significance.

CONCLUSIONS

Reported events of the two influenza vaccine types used were similar than in other seasons and consistent with their safety profiles.

Active surveillance of 2017 seasonal influenza vaccine safety: an observational cohort study of individuals aged 6 months and older in Australia

OBJECTIVE

To actively solicit adverse events experienced in the days following immunisation with quadrivalent inactivated influenza vaccine using Australia's near real-time, participant-based vaccine safety surveillance system, AusVaxSafety.

DESIGN AND SETTING

Observational cohort study conducted in 194 sentinel surveillance immunisation sites (primary care, hospital and community-based clinics) across Australia.

PARTICIPANTS

Individuals aged ≥6 months who received a routine seasonal influenza vaccine at a participating site (n=102 911) and responded to a survey (via short message service or email) sent 3 days after vaccination about adverse events experienced (n=73 892; 71.8%).

MAIN OUTCOME MEASURE

Near real-time and cumulative participant-reported rates of any adverse event, fever or medical attendance experienced within 3 days after vaccination overall, by brand, age, pregnancy status and concomitant vaccine receipt.

RESULTS

Participant median age was 57 years (range: 6 months to 102 years); 58.1% (n=42 869) were female and 2.7% (n=2018) were pregnant. Near real-time fast initial response cumulative summation and Bayesian analyses of weekly event rates did not demonstrate a safety signal. Children aged 6 months to 4 years had higher event rates (522/6180; 8.4%) compared with older ages; participants aged ≥65 years reported fewer events (1695/28 154; 6.0%). There were no clinically significant differences in safety between brands, by age group or overall. Cumulative data analysis demonstrated that concomitant vaccination was associated with increased rates of fever (2.1% vs 0.8%) and medical attendance (0.8% vs 0.4%), although all rates were low and did not exceed expected levels.

CONCLUSIONS

Novel, postmarketing AusVaxSafety surveillance demonstrated comparable and expected safety outcomes for the 2017 quadrivalent inactivated influenza vaccine brands used in Australia. These near real-time, participant-reported data are expected to encourage confidence in vaccine safety and promote uptake.