Focus: COVID vaccine effects wane over time but still prevent death

Several countries are now offering third COVID-19 shots amid reports of vaccines proving less effective over time. But do these countries really need to embark on widespread booster campaigns? Here’s what research tells us so far about how vaccines are performing.

One study suggests that after four months of the second dose, the Pfizer/BioNTech vaccine is less effective at preventing infection (classified as a positive PCR test), with protection falling from 96% to 84%. However, the research is a preprint, meaning that its results have yet to be formally reviewed by other scientists.

Similarly, real-life data from Israel suggests that over-60s who received their second dose of the Pfizer vaccine in March 2021 were 1.6 times better protected against infection than those who received their second dose two months earlier. However, the data was less clear cut when looking across other age groups. This study also hasn’t yet been peer reviewed.

Data for the Moderna vaccine shows that functional antibodies (those able to stop viruses from entering cells) persisted in most people for six months after vaccination. However, there was a gradual decrease in performance against the beta...