The PITCH study compared short (2-5 weeks) and long (6-14 weeks) dosing schedules of the Pfizer vaccine in 503 healthcare workers.
"We found that for people getting the longer dosing interval, antibodies fell over the 10 weeks after the first dose, but T cell levels were well-maintained. We know that a single dose of vaccine gives significant protection against COVID-19, so T cells may be an important part of the mechanism.
The long dosing interval resulted in 2x higher neutralising antibodies against all variants of the virus tested, including the Delta variant, compared to the short dosing interval. Absolute numbers of T cells to spike were lower after the long interval compared to the short one, but the T cell response had more characteristics of a helper response promoting long term memory and antibody production.
Regardless of the dosing schedule, the study found levels of antibodies and T cells varied from person to person, which may depend on genetics, underlying health conditions, and past exposure to COVID-19 and other viruses. This means our study is more relevant at a population level than for individual people, and underlies the importance of everyone getting two doses of the COVID-19 vaccine to maximise their own protection, particularly against Variants of Concern".
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