RESUMEN
With much of the world infected with or vaccinated against SARS-CoV-2, understanding the immune responses to the SARS-CoV-2 spike (S) protein in different situations is crucial to controlling the pandemic. We studied the clinical, systemic, mucosal, and cellular responses to two doses of SARS-CoV-2 mRNA vaccines in 62 individuals with and without prior SARS-CoV-2 exposure that were divided into three groups based on serostatus and/or degree of symptoms: Antibody negative, Asymptomatic, and Symptomatic. In the previously SARS-CoV-2-infected (SARS2-infected) Asymptomatic and Symptomatic groups, symptoms related to a recall response were elicited after the first vaccination. Anti-S trimer IgA and IgG levels peaked after 1st vaccination in the SARS2-infected groups, and were higher that the in the SARS2-naive group in the plasma and nasal samples at all time points. Neutralizing antibodies titers were also higher against the WA-1 and B.1.617.2 (Delta) variants of SARS-CoV-2 in the SARS2-infected compared to SARS2-naive vaccinees. After the first vaccination, differences in cellular immunity were not evident between groups, but the AIM+ CD4+ cell response correlated with durability of humoral immunity against the SARS-CoV-2 S protein. In those SARS2-infected, the number of vaccinations needed for protection, the durability, and need for boosters are unknown. However, the lingering differences between the SARS2-infected and SARS2-naive up to 10 months post-vaccination could explain the decreased reinfection rates in the SARS2-infected vaccinees recently reported and suggests that additional strategies (such as boosting of the SARS2-naive vaccinees) are needed to narrow the differences observed between these groups.
RESUMEN
Although there have been many studies on antibody responses to SARS-CoV-2 in breastmilk, very few have looked at the fate of these in the baby. We carried out a study in 22 mother/baby pairs (mothers who breastfed and who were SARS-CoV-2 vaccinated before or after delivery) looking at mother blood, mother milk, baby blood, baby nose, and baby stool. Breastfed infants only acquired systemic anti-SARS-CoV-2 IgG antibodies if their mothers were vaccinated antepartum. None of the infants had SARS-CoV-2-specific IgA in the blood, but surprisingly, half of the infants in the Antepartum group had high titer SARS-CoV-2-specific IgA in the nose that exceeded titers found in breastmilk. Vaccination antepartum followed by breastfeeding appears to be the best way to provide systemic and local anti-SARS-CoV-2 antibodies for infants.