COVID-19 booster shots do not suggest that vaccines are ineffective.
In the U.K., booster shots are currently available for those aged 50 and over, those who are immunocompromised, people working in health and social care, or those who live with someone who is clinically vulnerable.
As the Centers for Disease Control and Prevention (CDC) notes on its FAQ page, COVID-19 vaccines are working well in preventing deaths and hospitalizations caused by COVID-19. In September 2021, the CDC found that COVID-19 vaccines were between 71 and 92 percent effective in preventing hospitalization caused by the virus.
However, there has been some evidence showing declining protection against COVID-19 among some specific age groups. The CDC explains that people with compromised immune systems are especially vulnerable to moderate to severe side effects of COVID-19, and may not build up as strong an immune response. As such, it recommends a third booster shot following a second dose of the Pfizer-BioNTech COVID-19 vaccine or Moderna COVID-19 vaccine.
Guidance on the need for booster shots generally varies. In a statement from October 2021, The World Health Organization (WHO) acknowledged a slight decline in vaccine effectiveness in mild forms of the disease over a period of time. However, it said policies regarding booster shots should be "rigorously data driven" and take into account the global supply of vaccines as a whole. WHO said that most COVID-19 infections are still among the unvaccinated and that ensuring that most people are vaccinated should take priority over introducing booster shots.
It is incorrect to state that the booster vaccine shots suggest that COVID-19 vaccines do not work. Booster shots have been recommended for some age groups to increase immunity, but vaccines are still highly effective against preventing serious cases of COVID-19.