Vaccine Effectiveness against Influenza in 2015/16 in Hospital and Ambulatory Medical Care Facilities: Polish Results of the European I-MOVE+ Multicenter Study

Surveillance of medically-attended influenza in elderly patients from Romania-data from three consecutive influenza seasons (2015/16, 2016/17, and 2017/18)

Background

Influenza is an acute infection affecting all age groups; however, elderly patients are at an increased risk. We aim to describe the clinical characteristics and the circulation of influenza virus types in elderly patients admitted for severe acute respiratory infection (SARI) to a tertiary care hospital in Bucharest, Romania, part of the I‐MOVE+ hospital network.

Methods

We conducted an active surveillance study at the National Institute for Infectious Diseases “Prof. Dr Matei Balș,” Bucharest, Romania, during three consecutive influenza seasons: 2015/16, 2016/17, and 2017/18. All patients aged 65 and older admitted to our hospital for SARI were tested for influenza by PCR.

Results

A total of 349 eligible patients were tested during the study period, and 149 (42.7%) were confirmed with influenza. Most patients, 321 (92.5%) presented at least one underlying condition at the time of hospital admission, the most frequent being cardiovascular disease, 270 (78.3%). The main influenza viral subtype circulating in 2015/16 was A(H1N1)pdm09, followed by A(H3N2) in 2016/17 and B influenza in 2017/18. Case fatality was highest in the 2015/16 season (3.7%), 0% in 2016/17, and 1.0% in 2017/18. Vaccination coverage in elderly patients with SARI from our study population was 22 (6.3%) over the three seasons.

Conclusions

Our study has highlighted a high burden of comorbidities in elderly patients presenting with SARI during winter season in Romania. The influenza vaccine coverage rate needs to be substantially increased in the elderly population, through targeted interventions.

The Use of Test-negative Controls to Monitor Vaccine Effectiveness: A Systematic Review of Methodology

BACKGROUND

The test-negative design is an increasingly popular approach for estimating vaccine effectiveness (VE) due to its efficiency. This review aims to examine published test-negative design studies of VE and to explore similarities and differences in methodological choices for different diseases and vaccines.

METHODS

We conducted a systematic search on PubMed, Web of Science, and Medline, for studies reporting the effectiveness of any vaccines using a test-negative design. We screened titles and abstracts and reviewed full texts to identify relevant articles. We created a standardized form for each included article to extract information on the pathogen of interest, vaccine(s) being evaluated, study setting, clinical case definition, choices of cases and controls, and statistical approaches used to estimate VE.

RESULTS

We identified a total of 348 articles, including studies on VE against influenza virus (n = 253), rotavirus (n = 48), pneumococcus (n = 24), and nine other pathogens. Clinical case definitions used to enroll patients were similar by pathogens of interest but the sets of symptoms that defined them varied substantially. Controls could be those testing negative for the pathogen of interest, those testing positive for nonvaccine type of the pathogen of interest, or a subset of those testing positive for alternative pathogens. Most studies controlled for age, calendar time, and comorbidities.

CONCLUSIONS

Our review highlights similarities and differences in the application of the test-negative design that deserve further examination. If vaccination reduces disease severity in breakthrough infections, particular care must be taken in interpreting vaccine effectiveness estimates from test-negative design studies.

Detection of Influenza in the Epidemic Season 2016/2017 Based on I-MOVE+ Project

In the influenza season 2016/2017 in Europe, the predominant virus was A/H3N2/. In Poland, the percentage of people vaccinated against influenza was 3.33%. European I-MOVE+ project shows how important it is to monitor the effectiveness of influenza vaccine. The project demonstrates that a match between the circulating vaccine strains and those included in the vaccine for the Northern Hemisphere was low-to-moderate. In the present study, there were 379 patients and 296 control subjects examined in hospitals in Poland as part of I-MOVE+ project. The real-time reverse transcription polymerase chain reaction (qRT-PCR) method was used to detect the influenza virus in all subjects. We detected the influenza subtype A/H3N2/ in 59.1% and type B virus in 2.1%. There was one co-infection of subtype A/H3N2/ with subtype A/H1N1/ and eight co-infections of type B with subtype A/H3N2/. No influenza viruses were detected in the control group. Only 19 patients and 22 control subjects were vaccinated during the epidemic season in question. A proportion of people vaccinated against influenza in Poland remains dismally low compared to other European countries.