Impact of Nutritional Status on Antibody Titer After Booster mRNA COVID-19 Vaccine Among Elderly Adults in Japan.

Background Published studies on mRNA coronavirus disease 2019 (COVID-19) vaccine effects focus on younger individuals, comprising the majority of the workforce. Studies in elderly adults are sparse. Methods In total, 107 subjects were recruited (median age 78; interquartile range [IQR], 58.5–90.5; range, 35–105 years). Factors associated with antibody titer after the third mRNA COVID-19 vaccination were compared between 49 elderly (age ≥80; median, 94; IQR, 86–97; range, 80–105 years) and 58 younger (age ≤79; median, 61; IQR, 46–71; range, 35–79 years) adults. Results Among body mass index (BMI) categories, the group of underweight elderly adults had a lower antibody titer compared to those with normal weight (P <.01 after 1, 3, and 5 months). Elderly adults were less likely to maintain effective antibody titer (≥4160 AU/mL) compared to younger adults: 76% versus 98%, P <.001 after 1 month, and 45% versus 78%, P <.001 after 3 months. Elderly adults who maintained effective antibody titer for 5 months had a higher BMI (22.9 kg/m² vs 20.1 kg/m², P =.02), and were less likely to have underweight BMI (0% vs 31%, P =.02) compared to the subjects who failed to maintain effective antibody titer. Conclusions These results highlight the impact of nutritional status and the deleterious effect of underweight BMI on antibody titer and its maintenance among elderly adults following booster mRNA COVID-19 vaccination. [ABSTRACT FROM AUTHOR]