Interim Effectiveness Estimates of 2023 Southern Hemisphere Influenza Vaccines in Preventing Influenza-Associated Hospitalizations - REVELAC-i Network, March-July 2023

Influenza vaccine effectiveness against medically-attended influenza infection in 2023/24 season in Hangzhou, China

From 2020, influenza viruses circulation was largely affected by the global coronavirus disease (COVID-19) pandemic, notably leading to the extinction of the B/Yamagata lineage and raising questions about the relevance of the quadrivalent influenza vaccine, which includes this lineage. Evaluating vaccine effectiveness (VE) against influenza infections is important to inform future vaccine programs. A test-negative case-control study was conducted in five tertiary hospitals in Hangzhou, the capital city of Zhejiang province, China, enrolling medically-attended patients aged >6 months who presented with influenza-like illness (ILI) from October 1, 2023, to March 31, 2024. The VE was estimated using multivariate logistic regression models adjusted for sex, age, influenza detection methods, and influenza testing timing. Of the 157,291 medically-attended ILI participants enrolled 56,704 (36%) tested positive for influenza. Adjusted overall VE against any medically-attended influenza infection was 48% (95% Confidence interval [CI]: 46%-51%). The overall VE of the trivalent inactivated influenza vaccine (IIV3) was 59% (95% CI: 50%-66%), followed by the trivalent live attenuated vaccine (LAIV3) (VE = 53%, 95% CI: 42%-62%) and quadrivalent inactivated influenza vaccine (IIV4) (VE = 47%, 95% CI: 45%-50%). IIV3 provided even better protection against medically-attended influenza B infection than IIV4 (VE = 87%, 95% CI: 81%-92% for IIV3 versus VE = 53%, 95% CI: 50%-57% for IIV4). In the 2023/24 season in Hangzhou, China, the influenza vaccine offered moderate protection during a major epidemic. The results supported the World Health Organization recommendation to exclude the B/Yamagata lineage antigen in quadrivalent influenza vaccines in 2023.

Comparison of Two Field Deployable PCR Platforms for SARS-CoV-2 and Influenza A and B Viruses' Detection

BACKGROUND

Respiratory viral infections are a major public health challenge and the most diagnosed medical condition, particularly for individuals living in close proximity, like military personnel. We compared the sensitivity and specificity of the Biomeme FranklinTM and Truelab® RT-PCR thermocyclers to determine which platform is more sensitive and specific at detecting SARS-CoV-2 and influenza A and B viruses.

METHODOLOGY

RNA extracted from nasopharyngeal swabs of infected and uninfected individuals was tested on the Biomeme FranklinTM at Lackland and the Truelab® at Wright Patterson Air Force bases.

RESULTS

We found an 88% and 71% positivity rate in SARS-CoV-2-infected samples tested on Biomeme and Truelab®, respectively. Likewise, we found a 49% and 80% positivity rate in influenza-positive samples tested on Biomeme and Truelab®, respectively. One hundred percent of uninfected swab samples tested negative for SARS-CoV-2 on both platforms. Conversely, 91% and 100% of uninfected swabs tested negative for flu on Biomeme and Truelab®, respectively.

SIGNIFICANCE

Differences in specificity and sensitivity in detection of SARS-CoV-2 and influenza between Biomeme and Truelab® suggest that Truelab® is a more promising and potentially deployable diagnostic platform for SARS-CoV-2 and influenza viruses' detection in an austere environment.

Real-world effectiveness of influenza vaccine against medical-attended influenza infection during 2023/24 season in Ili Kazakh Autonomous Prefecture, China: A test-negative, case-control study

In the post-COVID-19 pandemic era, influenza virus infections continuously lead to a global disease burden. Evaluating vaccine effectiveness against influenza infection is crucial to inform vaccine design and vaccination strategy. In this study, we recruited 1120 patients with influenza-like illness (ILI) who attended fever clinics of 4 sentinel hospitals in the Ili Kazakh Autonomous Prefecture, Xinjiang Uygur Autonomous Region, China, from January 1 to April 7, 2024. Using a test-negative design, we estimated influenza vaccine effectiveness (VE) of 54.7% (95% CrI: 23.7, 73.1) against medical-attended influenza infection, with 62.3% (95% CrI: 29.3, 79.8) against influenza A, and 51.2% (95% CrI: 28.7, 83.0) against influenza B. Despite the moderate VE estimated in this study, influenza vaccination remains the most important approach to prevent influenza at the community level.

Establishing the African region monitoring vaccine effectiveness (AFRO-MoVE) network for respiratory pathogens

Population-level vaccination with newly developed vaccines to respond to the COVID-19 pandemic created a need to monitor vaccine effectiveness (VE) in the context of emerging SARS-CoV-2 variants and changing epidemiology. WHO and partners launched the African Region Monitoring Vaccine Effectiveness (AFRO-MoVE) Network in March 2021 to assess the performance of COVID-19 vaccines in real-world conditions in Africa. The Network aimed to facilitate and support comparable COVID-19 vaccine effectiveness studies in the African region, to provide a platform of scientific expertise and infrastructure, encourage the use of robust similar study designs to enable pooling to produce regional VE estimates and to build a sustainable network of hospitals, institutions, and experts to evaluate vaccines against pandemic and endemic respiratory pathogens. In the two years since its inception, the network has coordinated VE studies in the region and provided technical guidance and generic protocols employing robust methodologies. It brought together over 200 experts, representing 22 African countries and 55 organisations, and strengthened capacities by hosting ten webinars and six technical workshops. Of the 55 partners organisations, 25 based in 13 countries collaborated on implementing VE studies in the region. AFRO-MoVE supported study implementation in two phases, first targeting COVID-19 vaccination priority groups, then the general population. The network provides technical and financial support to nine studies, including three cohort studies in health workers and adults with comorbidities, and six test-negative design studies evaluating VE against symptomatic and severe disease. A data platform was established for pooled regional estimates. The AFRO-MoVE Network can form a sustainable platform to provide data for evidence informed decisions and timely VE monitoring for existing and new vaccines against respiratory pathogens and other diseases in the African region. Further development and consolidation of the network's activities can enable rapid response to future epidemics and pandemics.

Influenza virus circulation and vaccine effectiveness during June 2021-May 2023 in Thailand

Thai Ministry of Public Health recommends influenza vaccination for certain risk groups. We evaluated 2023 Southern Hemisphere influenza vaccine effectiveness against medically attended influenza using surveillance data from nine Thai hospitals and a test-negative design. During June 2022-May 2023, influenza vaccine provided moderate protection against seeking care for influenza illness (adjusted vaccine effectiveness 51%; 95% confidence interval 28-67). Understanding vaccine effectiveness can help guide future antigen selection and support clinicians to make a strong influenza vaccine recommendation to patients.

Impact of the COVID-19 Pandemic on Influenza Vaccination Coverage of Healthcare Personnel in Alicante, Spain

Influenza is a health problem and vaccination is the most effective measure to prevent it. The objective of this study was to evaluate the impact of the COVID-19 pandemic on vaccination coverage (VC) against influenza in healthcare workers (HCWs). A cross-sectional study was conducted at the Dr. Balmis University General Hospital in the province of Alicante (Spain), in which vaccination data were collected retrospectively. Adverse effects (AEs) were detected via telephone call between 15 and 30 days after vaccination. The existence of significant changes in VC between the different seasons studied was evaluated using Chi square with a statistical significance level of p < 0.05. A total of 8403 HCWs vaccinated throughout the different seasons were studied. The vaccination coverage of HCWs for influenza pre-COVID-19 pandemic (2019/20 season) was 51.9%; increased during the pandemic to 67.9% (2020/21 season) and 65.5% (2021/22 season); and, after the pandemic, it decreased to 42.7% (2022/23 season) (p < 0.05). The most frequent reason for vaccination during the periods evaluated was "self-protection", followed by "protection of patients" and "protection of family members". Of all HCWs evaluated, 26.6% (1460/5493) reported at least one AE. During the COVID-19 pandemic, HCWs' influenza vaccination coverage fluctuated considerably. There has been an increase in VC during the most critical moments of the pandemic, both in the 2020/21 and 2021/22 seasons, which has, subsequently, decreased in the 2022/2023 season, to levels below pre-pandemic (2019/2020 season), which justifies implementing specific measures to recover VC in Spain.

Interim Influenza Vaccine Effectiveness Against Laboratory-Confirmed Influenza - California, October 2023-January 2024

Surveillance data can provide rapid, within-season influenza vaccine effectiveness (VE) estimates to guide public health recommendations. Mandatory reporting of influenza vaccine administration to California's immunization information registry began January 1, 2023, and mandatory reporting of all influenza laboratory test results, including negative results, was instituted in California on June 15, 2023. These data, collected by the California Department of Public Health during October 1, 2023-January 31, 2024, were used to calculate interim influenza VE against laboratory-confirmed influenza by comparing the odds of vaccination among case-patients (persons who received a positive influenza laboratory test result) and control patients (those who received a negative influenza laboratory test result). VE was calculated as 1 - adjusted odds ratio using mixed-effects logistic regression, with age, race, and ethnicity as fixed effects and specimen collection week and county as random effects. Overall, during October 1, 2023-January 31, 2024, estimated VE was 45% among persons aged ≥6 months, 56% among children and adolescents aged 6 months-17 years, 48% among adults aged 18-49 years, 36% among those aged 50-64 years, and 30% among those aged ≥65 years. Consistent with some previous influenza seasons, influenza vaccination provided moderate protection against laboratory-confirmed influenza among infants, children, adolescents, and adults. All persons aged ≥6 months without a contraindication to vaccination should receive annual influenza vaccination to reduce influenza illness, severe influenza, and strain on health care resources. Influenza vaccination remains the best way to prevent influenza.