New studies have shown that booster doses of Pfizer and Moderna vaccines provide enhanced protection against severe infection from coronavirus variants that require hospitalization.

Data released by the U.S. Centers for Disease Control and Prevention on Friday revealed that a third dose of either vaccine is over 90 percent effective against both the Delta and Omicron variants.

Studies found that the effectiveness of two vaccine doses drops to 57 percent after six months.

U.S. officials urged people to get a booster dose of the vaccine when they become eligible.

According to the CDC study, vaccine effectiveness against worsening health requiring hospitalization after two doses was 90 percent and lasted up to six months after the second dose but dropped to 81% thereafter.

Two weeks after the third dose, vaccine protection from the likelihood of worsening health and hospitalization rose to 94 percent.

During the recent surge in Omicron cases, the effectiveness rate of two vaccine doses was 81 percent two weeks after receiving the second dose and up to six months later, before subsequently falling to 57%. Two weeks after the third dose, the effectiveness increased to 90 percent.

The U.S. study was based on data from 88,000 hospital admissions across 10 U.S. states.

A second CDC study, also released on Friday, examined data from 25 state-level health departments and found that people who received a third booster dose were less likely to contract Omicron infection.

The research also found that among patients who received boosters, there was an average of 149 cases per 100,000 people, compared to 255 cases among those who had only received two doses so far.

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A separate study published in the Journal of the American Medical Association found that the likelihood of contracting COVID-19 and showing symptoms was 66 percent lower for those who received a booster dose.

The spread of the Omicron variant has led to a record number of hospital admissions in the United States. The number of patients currently hospitalized in the country exceeds 150,000, surpassing the previous record set in January 2021.

In the Northeast, including New York and the capital Washington, hospital admissions have decreased, prompting some experts to speculate that the number of Omicron infections has peaked in some areas.

However, officials warn that other parts of the United States may still be several weeks away from peak before the number of infections starts to decline.

Earlier this week, U.S. President Joe Biden was asked why the definition of "fully vaccinated" was not changed to mean receiving three vaccine doses instead of two.

Biden replied: "You are better protected with the booster (third dose). And it’s all part of the same idea."