Humoral Response after Vaccination with Half-Dose of BNT162b2 in Subjects under 55 Years of Age

In the context of the ongoing COVID-19 pandemic, using a half-dose schedule vaccination can help to return to normalcy in a cost-efficient manner, which is especially important for low and middle-income countries. We undertook a study to confirm that in adults up to 55 years old, the humoral response to the half-dose (15 µg, 35 participants between 18 and 55 years old) and to the recommended dose (30 µg, 155 participants) in the two-dose three-week interval schedule would be comparable. Antibody levels were measured by the Elecsys Anti-SARS-CoV-2 S assay (Roche Diagnostics, upper detection limit: 2570 BAU/mL) on the day of dose 2 of the vaccine and then 8–10 days later to assess peak response to dose 2. The difference in proportions between the participants who did and did not exceed the upper detection limit 8–10 days after dose 2 was not statistically significant (p = 0.152). We suggest that a half-dose schedule can help to achieve widespread vaccination coverage more quickly and cheaply.