LAUSR

The efficacy of one dose Ad5-nCoV has been concerning. This study aimed to evaluate the effect of a single dose BNT162b2 in individuals after a completed Ad5-nCoV vaccination regiment compared to a group without this boost measuring SARS-CoV-2 Spike 1–2 IgG antibodies in plasma. This observational study included a subgroup analysis of patients who were immunized with Ad5-nCoV in a northern city of Mexico. During follow-up, some patients self-reported having received a BNT162b2 booster. We report baseline IgG levels, 21–28 days after the Ad5-nCoV dose, three months, and an additional 21–28 days after BNT162b2 (four months after Ad5-nCoV). Seventeen patients, age 40 (16), 52.9% men, were analyzed. We created four groups: G1 and G2 refer to patients without a history of SARS-CoV-2 infection, vaccinated with Ad5-nCoV and Ad5-nCoV/BNT162b2 (n = 4 and n = 6), respectively; G3 and G4 included patients with a history of SARS-CoV-2 infection and immunized with Ad5-nCoV and Ad5-nCoV/BNT162b2 (n = 5 and n = 2), respectively. The Ad5-nCoV/BNT162b2 protocol reported higher antibody titers after 21–28 days. Median (IQR) values were: G1 46.7 (-), G2 1077.5 (1901), G3 1158.5 (2673.5), and G4 2090 (-) (p < 0.05). Headache and pain at injection site were the most frequent adverse reactions associated with Ad5-nCoV (n = 10, 83%) and BNT162b2 (n = 5, 83.3%), respectively. Patients receiving BNT162b2 after Ad5-nCoV had higher SARS-CoV-2 spike 1–2 IgG antibody titers and had no severe adverse reactions.