How much protection a fourth dose can provide hasn’t been studied enough, medics told CNBC.
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The Food and Drug Administration said Thursday vaccine makers should update their Covid-19 booster shots to target the latest Omicron subvariants gaining ground in the United States
dr Peter Marks, head of the FDA’s vaccine division, said manufacturers should update their trials to target Omicron BA.4 and BA.5 in addition to the original virus strain that first emerged in Wuhan, China, in 2019.
The FDA’s panel of independent experts on Tuesday voted overwhelmingly to recommend a vaccine switch after a day-long meeting at which they assessed the pros and cons of updating the immunizations.
Vaccine manufacturers are struggling to keep up with the rapid evolution of the virus. Pfizer and Moderna developed their Omicron syringes to adapt to the original version of the BA.1. which caused the massive wave of infections over the winter.
However, BA.1 has been superseded by other Omicron subvariants and is no longer in circulation in the United States. Omicron BA.4 and BA.5 now account for more than 50% of US Covid infections, according to the Centers for Disease Control and Prevention.
Pfizer and Moderna on Tuesday presented clinical trial data showing that their updated vaccines elicited a stronger immune response against Omicron BA.1 than the original version of the vaccines, which was based only on the strain found in Wuhan. The updated vaccinations based on BA.1 did not perform as well against BA.4 and BA.5, although the immune response was still robust.
However, the studies were small, with only a few hundred participants, and there is currently no data on how well the recordings will work in the real world. Immune response is generally considered a good indicator of how well vaccines protect against disease.
It’s unclear how long it will be before vaccine makers shift gears and develop shots that contain BA.4 and BA.5. Marks said the FDA has asked the companies to start clinical trials with these newer subvariants.
The two-dose primary series will not change for the time being, Marks said. The FDA wants to update booster shots to provide more durable protection before the fall, when public health experts expect another wave of infections as immunity to the vaccines wanes and people head indoors to escape the weather. Covid spreads more easily indoors.
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