Single-dose BNT162b2 mRNA COVID-19 vaccine significantly boosts neutralizing antibody response in health care workers recovering from asymptomatic or mild natural SARS-CoV-2 infection

•SARS-CoV-2 neutralizing antibody (NtAb) titres in health care workers (HCWs).•After 313 days from a mild, asymptomatic infection NtAbs are often still detectable.•One vaccination dose strongly boosts NtAb titers in previously infected HCWs.•One dose boosts NtAbs in previously infected more than two doses in uninfected HCWs.•Second dose significantly boosts NtAbs elicited by first dose in uninfected HCWs.