Many U.S. Marines' hesitancy to receive coronavirus vaccinations could prove to be a sticking point for President Biden as some Democrats pressure him to mandate vaccinations for service members.

Nearly 40% of U.S. Marines who have been offered the coronavirus vaccine declined, according to data released last week. That translates to approximately 75,500 Marines who have received the vaccine, and approximately 48,000 who have declined the vaccine. More than 100,000 Marines have yet to be offered the coronavirus vaccine, however.

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"We fully understand that widespread acceptance of the COVID-19 vaccine provides us with the best means to defeat this pandemic. The key to addressing this pandemic is building vaccine confidence. The vaccine is voluntary for all personnel at this time because the vaccines are authorized under an Emergency Use Authorization from the Food and Drug Administration," Marine Corps spokesman Capt. Andrew Wood told Fox News in a statement.

Walgreens pharmacist Brandon Berger checks syringes before administering second doses of the Pfizer COVID-19 vaccine to seniors at John Knox Village, Tuesday, Feb. 9, 2021, in Pompano Beach, Fla. (Amy Beth Bennett/South Florida Sun-Sentinel via AP)

Walgreens pharmacist Brandon Berger checks syringes before administering second doses of the Pfizer COVID-19 vaccine to seniors at John Knox Village, Tuesday, Feb. 9, 2021, in Pompano Beach, Fla. (Amy Beth Bennett/South Florida Sun-Sentinel via AP)

In March, seven Democratic lawmakers led by Rep. Jimmy Panetta of California, sent a letter to President Biden requesting he issue a "waiver of informed consent" that would essentially mandate members of the military receive coronavirus vaccinations, Navy Times reported.

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"Vaccinating every eligible servicemember will improve readiness and have an immediate and positive impact on the communities in which they serve," Panetta said according to Navy Times. "Requiring DOD to obtain informed consent prior to vaccination is not only harmful to our national security, but contrary to the best interests of servicemembers, their families, communities and colleagues."

Military leadership has honed in on the issue. Air Force Maj. Gen. Jeff Taliaferro, vice director of operations for the Joint Staff, told Congress in February that "very early data" suggests that just up to two-thirds of the service members offered the vaccine have accepted.

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That’s higher than the rate for the general population, which a recent survey by the Kaiser Family Foundation put at roughly 50%. 

Service leaders have vigorously campaigned for the vaccine. They have held town halls, written messages to the force, distributed scientific data, posted videos, and even put out photos of leaders getting vaccinated.

Many Americans have expressed their fears of a so-called vaccine passport that would dictate what Americans are allowed to do, although there's no sign such a system will be instituted. Nevertheless, some private entities are requiring students to receive coronavirus vaccinations, including colleges like Oakland University in Michigan, Cornell University in upstate New York, Rutgers University in New Jersey, and Brown University in Rhode Island.

The Associated Press contributed to this report.