Thanks for posting that. So it was just a one-liner from the TV presenter then, I'd be interested to hear if
@ilovewings gets a reply to the email she sent them.
From all the searching I've done on this I can't find reference to any studies that back this up, most seem to start measuring 7-14 days after.
This article published by Pfizer -->
Pfizer and BioNTech Announce Phase 3 Trial Data Showing High Efficacy of a Booster Dose of Their COVID-19 Vaccine | Pfizer says "Symptomatic COVID-19 occurrence was measured from at least 7 days after booster or placebo, with a median follow-up of 2.5 months."
This from the BMJ -->
Covid-19: Booster vaccine gives “significant increased protection” in over 50s says "two weeks after receiving the booster dose, protection against symptomatic infection increased to 93.1% (95% confidence interval, 91.7 to 94.3) in those who initially had two doses of the Oxford AstraZeneca vaccine, and 94.0% (95% CI, 93.4 to 94.6) for those who had Pfizer."
I don't think it's safe therefore to assume an immediate effect from the booster without more information to back that statement up. JMO.