Sustained Maternal Antibodies Against Parechovirus‐A3 During the Coronavirus Disease 2019 Pandemic

The epidemiology of parechovirus-A3 (PeV-A3) infection in neonates and young infants changed during the coronavirus disease 2019 (COVID-19) pandemic. We hypothesized the pandemic impacted maternal antibodies against PeV-A3. To test this hypothesis, we measured neutralizing antibody titers (NATs) against PeV-A3 in 102 cord blood samples from full-term infants born in June-December 2023 at Niigata University Hospital in Niigata, Japan. Maternal data were collected and compared the findings with our previous pre-pandemic data. The median maternal age was 34.5 years (range: 30-37 years). The geometric mean titer (GMT) against PeV-A3 was 98.4 (95% confidence interval [CI]: 61.7-156.8). The GMT for ages 25-34 years (184.6, n = 45) and 35-44 years (56.3, n = 51) sustained at the same level when we compared to age-matched pre-pandemic data for ages 16-24 years (336.5, n = 11, p = 0.84) and 25-34 years (31.9, n = 107, p = 0.14), respectively. By multivariable logistic regression analyses, maternal age ≤ 34 years was associated with higher seropositivity (adjusted odds ratio [aOR] 3.12, 95% CI 1.18-8.78, p = 0.03). Maternal NATs against PeV-A3 were sustained at the same level during the COVID-19 pandemic, indicating intra-pandemic maintenance of humoral immunity to PeV-A3 in women of childbearing age.