Florian Kramer and others cite in the New England Journal of Medicine that the efficacy of two injections of the mRNA vaccines such as Moderna and Pfizer is high in preventing symptomatic SARS-CoV-2 infection in persons without previous coronavirus disease.  

However, they wondered what the response would be to the first vaccine dose in patients who had had previous COVID-19 infection.  

They looked at 110 study participants, 67 who were seronegative participants and found that repeated sampling of antibody levels after the first dose indicated that the majority of the seronegative participants had variable and relatively low SARS-CoV-2 IgG responses within 9-12 days post vaccination.  

This contrasted with participants with SARS-CoV-2 antibodies at baseline before the first vaccine injection who rapidly developed uniform high antibody titres within four days after vaccination.

They found that antibody titres of vaccinees with pre-existing immunity were 10 to 45 times as high as those vaccinees without pre-existing immunity at the same points after the first vaccine dose. 

They also found that the antibody titres of the vaccinees without pre-existing immunity increased by a factor of 3 after the second vaccine dose whereas no increase in antibody titres was observed in the COVID-19 survivors who received the second vaccine dose.

There was no substantial difference noted in the dynamics of antibody responses elicited by the Pfizer and Moderna vaccines after the first dose.

The authors concluded that a single dose of mRNA vaccine elicited a rapid immune response in seropositive participants with post-vaccination antibody titres that were similar to or exceeded titres found in seronegative participants who had received two vaccinations.  

However, they also questioned whether a single dose of mRNA vaccine was effective protection in seropositive persons and suggested that this required further investigation.

The London General Practice, the leading London doctors clinic in Harley Street commends the Government on its vaccination programme and encourages all those eligible to be vaccinated.

Dr Paul Ettlinger
BM, DRCOG, FRCGP, FRIPH, DOccMed

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