Approximately 1-8% of individuals do not develop antibodies following SARS-CoV-2 infection (sero-negatives). One BNT162b2 dose resulted in potent humoral response in 14 sero-negatives and 15 sero-positives, significantly higher than the response of 15 naïve-individuals, to two doses suggesting that COVID-19 provoked a memory response in individuals without detectable antibodies.

Clin Infect Dis.
Lustig Y, Mendelson E, Mandelboim M, Biber A, Levin EG, Cohen C, Regev-Yochay G, Schwartz E.
doi: 10.1093/cid/ciac196.