U.S. firm Pfizer Inc. has called for an additional third shot of its COVID-19 vaccine, citing new data showing its efficacy trails off after six months, but doctors remain unconvinced, saying that what’s more important now is to focus on inoculating those who haven’t received all of their shots yet.
Manufacturers of messenger RNA (mRNA) vaccines administered in Japan — Pfizer and its German partner BioNTech SE, as well as U.S. firm Moderna Inc. — have been developing booster shots in the belief that a third dose will be necessary sometime between six and 12 months after people get their second shot. The issue of additional shots comes amid an alarming spike in new infections globally, driven by the highly transmissible delta variant.
Pfizer’s clinical study — based on around 42,000 volunteers in six countries and published on the medRxiv preprint server for health sciences Wednesday — showed that the efficacy of the vaccine was 96.2% from seven days after a second dose. It then fell 6 points by two months after the second dose and another 6 points four months after, and finally to 83.7% in the four- to six-month period.
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