The U.S. Food and Drug Administration (FDA) supports changing Covid shots to target the most recent omicron sub-options

Health officials told CNBC that not enough research has been done on how much protection a fourth dose can provide.

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The Food and Drug Administration on Thursday said vaccine makers should update their Covid-19 booster shots to target the most recent omicron sub-options that are gaining momentum in the US.

Dr. Peter Marks, head of the FDA’s vaccine division, said manufacturers should update their vaccines to target omicron BA.4 and BA.5 in addition to the original strain of the virus that first emerged in Wuhan, China, in 2019.

The FDA wants to update booster shots to provide better protection before the fall, when public health experts expect a new wave of infections as vaccine immunity wanes and people hide indoors to escape the weather. Covid spreads more easily indoors.

Marks says the two-dose primary vaccination series will not change for now. In other words, fully vaccinated people will not start from scratch in the fall. They will simply receive an omicron inoculation to increase their protection against the virus. And people who haven’t been vaccinated yet will first get two doses of the original vaccine and then probably get a shot with the new version.

A panel of independent FDA experts on Tuesday voted overwhelmingly in favor of the vaccine change recommendation after a one-day meeting in which they assessed the advantages and disadvantages of updating vaccines ahead of the U.S. fall booster campaign.

Vaccine manufacturers are not keeping up with the rapid evolution of the virus. Pfizer and Moderna developed their omicron vaccines to target the original version of BA.1, which caused a massive winter infection wave that swept hospitals with sick patients.

But BA.1 has been superseded by other omicron sub-variants and is no longer circulating in the US. Omicrons BA.4 and BA.5 currently account for more than 50% of Covid infections in the US, according to the Centers for Disease Control and Prevention. Prevention.

It is not clear how long it will take for vaccine manufacturers to switch and develop vaccines that include BA.4 and BA.5 rather than the original version of omicron. Companies have been asked by the FDA to begin clinical trials of these new sub-options, Marks said. The FDA panel has generally preferred to target BA.4 and BA.5 to keep up with the evolution of the virus.

On Tuesday, Pfizer and Moderna released clinical trial data demonstrating that their updated vaccines elicit a stronger immune response against omicron BA.1 than the original versions of the vaccines that the FDA cleared in December 2020. The updated vaccinations are based on BA.1. , did not work as well against BA.4 and BA.5, although the immune response was still strong according to the data.

The studies have been small, with only a few hundred participants, and there is currently no data on how well shots will perform in the real world. The immune response is generally regarded as a good indicator of how well vaccines protect against disease.

Some members of the FDA panel have said more data is needed on the effectiveness of new vaccines before they are introduced. Other members of the group said it’s unclear what effect adding a new ingredient to vaccines could have on a form of heart inflammation called myocarditis. Pfizer and Moderna vaccines are associated with an increased risk of myocarditis after the second dose in adolescent boys. However, according to the CDC, covid infection is associated with a higher risk of myocarditis than vaccination.

All currently approved Covid vaccines are based solely on the original version of the virus that emerged in China over two years ago. Vaccines no longer provide the same level of protection against infections and minor illnesses because the virus has changed so much. They still generally prevent severe illness, although there are fears that this protection will also erode as the virus evolves.

The virus has a protein called a spike that it uses to enter human cells. Current vaccines use copies of the spike of the original version of the virus to elicit an immune response that protects against disease. The immune response sends out antibodies that recognize the outbreak of the virus and block it from invading human cells.

However, the antibodies triggered by the original vaccines have difficulty recognizing highly mutated versions of the spike on omicron sub-variants. In other words, omicron penetrates the protective walls erected by vaccines, causing infections and mild illness even in people who keep up with their vaccinations.