CNN
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An independent panel of experts advising the U.S. Food and Drug Administration on vaccine decisions will meet all day Thursday to consider what the future of Covid-19 vaccinations in the United States should look like.
Currently, there are two types of Covid-19 vaccines available in the United States. The first vaccines people received (also known as primary vaccine series) included a set of instructions to teach the immune system to fight off the original version of the virus that emerged in 2019.
The problem is that the index strain is no longer in circulation. A few months ago, it was overwhelmed by the ever-growing parade of new variants.
So last year, after consulting with its vaccine advisors, the FDA decided it was time to update the vaccine. These new bivalent lenses contain two sets of instructions; one to alert the immune system to the original version of the coronavirus, and the second to teach the immune system to recognize and fight the BA.4 and BA.5 subvariants of Omicron that emerged in the US last year.
Late last year, a new two-strain booster vaccine was recommended for people who had received the main series of vaccines, which account for nearly 70% of all Americans, to improve their protection against the latest variant of the virus.
But adoption of the new booster has been slow. Only 15% of people have gotten one since it was first offered in September.
A separate but related problem is that previously unvaccinated Americans — including infants and young children who have just reached the age of eligibility for the Covid-19 vaccine — are still being vaccinated against strains of the virus they are unlikely to encounter.
As a result, FDA advisers are expected to vote on Thursday on whether the U.S. should offer one type of Covid-19 vaccine for both primary and booster doses. The committee is also expected to consider how many strains of the virus should be included in the shot, and how and when those strains should be selected.
The idea is that most people will be urged to get the updated Covid-19 vaccine once a year, just like they get their flu shot. People who are unlikely to respond adequately to a single dose of the vaccine, such as the elderly or those with weakened immune systems, will be advised to get two doses a year, the same as people who are getting the Covid-19 vaccine for the first time.
Another big question the advisory committee might want to consider is how effective the dual-strain vaccine will be.
Early research on the effectiveness of these new vaccines has been mixed. Some argued that they provided better protection than the original single-strain vaccine, while others concluded that the protection was about the same.
On Wednesday, the US Centers for Disease Control and Prevention released one of the first real-world observations of the effectiveness of a bivalent booster against the Omicron subvariants BA.5 and XBB, as well as XBB.1.5.
Using the results of nearly 30,000 Covid-19 tests conducted at pharmacies, the study determined that on average, the bivalent booster cut the risk of symptomatic infection by about half, even for the rapidly spreading XBB.1.5 subvariant The same is true for the body. Protection against serious illness and death may be higher.
Another issue that an FDA advisory committee may consider is how safe the bivalent booster is.
The CDC and FDA said this month they had detected a potential safety signal for Pfizer’s booster. In a single medical records database from a large group of US hospital systems, the updated Pfizer booster was associated with an increased risk of stroke due to blood clots in people over the age of 65.
The CDC said it had looked — and failed to find — the same safety signal in other databases and in other countries where the Pfizer vaccine was used. It continues to update its assessment with new data, but the agency said this appears to be a statistical fluke and no changes to recommended vaccinations are needed at this time.
The session is scheduled to begin at 8:30 AM ET and will be open to the public via webcast.