Enhanced passive safety surveillance of high-dose and standard-dose quadrivalent inactivated split-virion influenza vaccines in Germany and Finland during the influenza season 2021/22

BACKGROUND

Enhanced passive safety surveillance (EPSS) was conducted for quadrivalent inactivated split-virion influenza vaccines (IIV4) in Germany (high dose [HD], aged ≥60 years) and in Finland (standard dose [SD], aged ≥6 months) at the beginning of the northern hemisphere 2021/22 influenza season. The primary objective was to assess adverse drug reactions (ADRs) occurring ≤7 days post-vaccination.

METHODS

Vaccinees were issued vaccination cards (VC) and were encouraged to report ADRs via an electronic data collection system or by telephone. ADRs were assessed by frequency, time to onset, intensity and by age group. The vaccinee reporting rate (RR) was calculated as the number of vaccinees reporting ≥1 ADR divided by total vaccinees. Reactogenicity was compared with previous experiences with each vaccine.

RESULTS

Among 903 HD-IIV4 vaccinees in Germany, 17 reported ≥1 ADR within ≤7 days post-vaccination: RR, 1.88% (95% CI: 1.10, 3.00). Time to onset was known for 53/65 ADRs, all of which occurred ≤7 days post-vaccination. In Germany, seven ADRs were reported that were not listed previously. Among the 1000 SD-IIV4 vaccinees in Finland, 49 reported ≥1 ADR within ≤7 days post-vaccination: RR, 4.90% (95% CI: 3.65, 6.43). Time to onset was known for 126/134 ADRs, of which 125 occurred ≤7 days post-vaccination. In Finland, 21 ADRs were reported that were not listed previously. No ADRs reported during follow-up were serious.

CONCLUSIONS

The EPSS for HD-IIV4 and for SD-IIV4 in the 2021/22 influenza season did not suggest any clinically relevant changes in safety beyond what is known/expected for IIV4s.

Enhanced passive safety surveillance of a quadrivalent inactivated split virion influenza vaccine in Finland during the influenza season 2020/21

BACKGROUND

The European Medicines Agency (EMA) requires enhanced safety surveillance to be conducted for annual seasonal influenza vaccines with the aim of rapidly detecting any potential new safety concerns before the peak immunisation period of the vaccine in any given year. The aim of this study was to detect any clinically significant change in the frequency or severity of expected reactogenicity of the quadrivalent inactivated split-virion influenza vaccine (IIV4) during routine immunisation in Finland for the 2020/21 season. The primary objective was to investigate the frequency of suspected adverse drug reactions (ADRs) occurring within 7 days following vaccination.

METHODS

Enhanced passive safety surveillance of individuals vaccinated with IIV4 was conducted from October 9, 2020 to November 30, 2020 across seven sites in Finland. The vaccinee reporting rate and ADR reporting rate were calculated and compared with known or expected safety data in order to identify any clinically significant changes.

RESULTS

Data were collected from 1008 individuals with 29 vaccinees reporting 82 suspected ADRs. Of these, 28 people reported 79 suspected ADRs within 7 days following vaccination, corresponding to a vaccinee reporting rate of 2.78% (95% CI: 1.85, 3.99) (ADR reporting rate, 7.84% [95% CI: 6.25, 9.67%]). The most frequently reported ADRs were injection site reactions (vaccination site pain, vaccination site erythema and vaccination site swelling) (n = 46, 2.28%), myalgia (n = 9, 0.89%) and headache (n = 8, 0.79%). No serious suspected adverse events were reported at any point post-vaccination and ADR reporting rates were in general lower compared to those reported for IIV4 in the 2019/20 surveillance study.

CONCLUSION

No clinically significant changes in what is known or expected for IIV4 were reported for the 2020/21 season which supports the safety profile of this vaccine and will help maintain public confidence in influenza vaccination.

Five-Year Antibody Persistence Following a Japanese Encephalitis Chimeric Virus Vaccine (JE-CV) Booster in JE-CV-Primed Children in the Philippines

We assessed antibody persistence following booster vaccination with a Japanese encephalitis chimeric virus vaccine (JE-CV; IMOJEV) in JE-CV–primed children. In an open phase 3 trial, 349 children in the Philippines, who received JE-CV 2 years previously, received a booster dose. JE neutralizing antibody titers were assessed (50% plaque reduction neutralization test) annually for up to 5 years after booster vaccination. Seroprotection rates (percentage of children with titers ≥10 [1/dil]) and geometric mean titers (GMTs) were, respectively, 98.2% and 161 after 5 years. JE-CV booster induced long-lasting anamnestic immune response in JE-CV–primed children, with high seroprotection rates and GMTs over the accepted threshold for serological protection (10 [1/dil]).

Persistence of Wild-Type Japanese Encephalitis Virus Strains Cross-Neutralization 5 Years After JE-CV Immunization

Background

The live-attenuated Japanese encephalitis (JE) vaccine (JE-CV; IMOJEV) induces a protective response in children. A shift in circulating JE virus strains suggests that a genotype shift phenomenon may occur throughout Southeast Asia. We assessed the neutralization of wild-type (WT) JE virus isolates at distal time points after vaccination.

Methods

We analyzed serum samples from a subset of 47 children who had received a JE-CV booster after an inactivated JE vaccine primary immunization. We measured antibody titers (50% plaque reduction neutralization test) using a panel of WT JE strains at baseline, then after the booster at 28 days and 6 months in all subjects present at the time points and in a subset at year 5. Three additional recent isolates were tested at year 5.

Results

Of 47 subjects, 43 (91.5%) subjects had JE neutralizing antibody titers ≥10 (reciprocal serum dilution) against the homologous strain before JE-CV boost; all were seroprotected up to year 5 after the JE-CV boost. Baseline WT seroprotection ranged between 78.7% and 87.2%; all subjects were seroprotected against the 4 WT strains at 28 days and 6 months; year 5 seroprotection ranged between 95.7% and 97.9%. Similar rates of protection against 3 additional WT isolates were observed at year 5.

Conclusions

The long-term immune responses induced after a JE-CV booster dose in toddlers were able to neutralize WT viruses from various genotypes circulating in Southeast Asia and India.

Clinical Trials Registration

NCT00621764.