Some vaccines, such as those for mumps and measles, ordinarily confer lifetime immunity. Other vaccines, such as the flu vaccine, require yearly injections.

To date, the Pfizer and Moderna COVID-19 vaccine has shown to be highly effective at preventing infections in real-world conditions, and the latest findings imply it should maintain its effectiveness over time.

However, the question remains, exactly how long will the vaccine protect against emerging variants of the virus. Will a booster shot be required, or will vaccines need to be tweaked.

In the 6-month status report, Pfizer-BioNTech said the ongoing phase 3 clinical trial of its mRNA vaccine shows that vital immunization persists for at least six months among vaccinated individuals.

The clinical trial found the vaccine to be 100 percent effective against severe disease as defined by the Centers for Disease Control and Prevention (CDC), and 95.3 per cent effective against severe COVID-19 as defined by the Food and Drug Administration (FDA).

The fact that COVID-19 vaccine effectiveness continued almost unchanged throughout the study period is good news and indicates that protection will be lasting.

As research continues, a clearer picture will emerge on how long immunity lasts after the COVID-19 vaccination. For the moment, the “guarantee” is longer than six months with no foreseeable immediate sharp decrease.