A study published on 11 July 2023 titled “The Effect of Third Dose of Pfizer/BioNTech and Moderna COVID-19 mRNA Vaccines on IgG Antibody Titers” by T.A. Khuc et al has found that the third dose doesn’t seem to work for long.
The study was relatively small. Of the 189 who enrolled, only 77 followed up to the end for analysis.
Participants provided a blood sample on the day of and before the administration of the third dose. Anti-SARS-CoV-2 immunoglobulin G (IgG) titer levels were assessed. Participants then returned at week 2, week 12 and week 24 after administration of the third dose to provide a blood sample for assessment.
Of the 77 participants, 32 (42%) were male and 45 (58%) were female. The average age was 51 years. Most participants received Pfizer.
The results:
“For the baseline blood draw, the average antibody titer was 39.34 AU/mL (SD=105.22).”
“Two weeks after the administration of the third dose, the mean number of antibody titers increased to 293.35 AU/mL (SD=331.93, p<0.0001).”
“…the average antibody titer at week 12 was 143.91 AU/mL (SD=137.69, p<0.0001).”
“The average antibody titer was 127.04 AU/mL (SD=139.94, p=0.0075) 24 weeks after the third dose.”
As for Pfizer and Moderna, there was no “significant difference”.
In short, the third dose works for a few weeks “before a significant decrease as measured at 24 weeks”. Nevertheless, the authors suggest “that over time, subsequent booster shots should be provided to promote continuous elevated IgG antibody titers for protection against the SARS-CoV-2 virus”. Right.
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