ourself from serious symptoms when you get infected and may also help to reduce the longer-term impact."
An estimated 2% of the U.K. population reported COVID symptoms lasting more than 4 weeks after infection as of Dec. 6, 2021, well into the Omicron wave of the pandemic.
According to a prior review of mobile app data tracking cases in U.S., U.K., and Swedish populations, symptoms persisted in up to 13% of infected individuals at 1 to 2 months and in 2.6% for 3 months or longer. Potentially more reliable data from clinic-based assessments suggested that 33% to 98% of survivors have symptoms for at least a month after infection.
The U.K. Health Security Agency analysis included a total of 15 studies of long COVID: four from the U.S., four from the U.K., two from India, two online with participants in multiple countries, and one each from France, Indonesia, and Israel. Full vaccination was universally considered two doses of a two-dose vaccine series or one of a single-dose vaccine.
The document cautioned that all of the studies considered were observational. "As there are many differences between people who are and are not vaccinated, there is a risk in all these studies that factors other than vaccination status may have influenced the results (in any direction)," it pointed out.
Additionally, the studies varied widely in their definition of long COVID, and the rapid review precluded pooled or meta-analysis of the findings together.
U.K. Health Security Agency
Source Reference: UKHSA COVID-19 Evidence Team "The effectiveness of vaccination against long COVID: A rapid evidence briefing" U.K. Health Security Agency 2022.