Why vaccinating the world against COVID-19 is a monumental undertaking.

COVID-19 vaccines were found to cut risk of heart failure by up to 55% and blood clots by up to 78% following COVID infection, according to a new study.

Researchers in the study looked at the original strain of the virus and the delta variant.

Vaccines are proven to reduce deaths and help end pandemics, but the historic speed that the coronavirus vaccines have been developed has made some people hesitant to take them.

Newly released survey data from the CDC shows 36 million American adults, about 13.9% of the U.S. adult population, has received the updated COVID vaccine.

With new flu and COVID-19 vaccines available, which one is the right one for you?

Older adults who got a COVID booster and a high-dose version of the flu vaccine together may have an increased risk of stroke, according to a new FDA-funded study.

Moderna announced the first participant has been dosed in the company's phase 3 clinical trial of its combination flu and COVID vaccine.

The latest poll conducted by the KFF COVID-19 Vaccine Monitor found that nearly half of all adults in the U.S. plan to get the newly recommended COVID-19 vaccine.

Immunity wanes after anywhere from 3-6 months, experts say.

ABCNL's Elizabeth Schulze sits with U.S. Surgeon General Dr. Vivek Murthy and our panel to discuss the resurgence of COVID and the new booster shot.

Florida's former surgeon general is speaking out against the DeSantis administration advising against updated COVID shots for people under 65.

Florida Gov. Ron DeSantis is advising against the use of the new COVID-19 booster for people under the age of 65, even as infections tick upward in the U.S.

The latest, updated COVID-19 vaccines should soon be available to everyone and offered largely free of cost, according to the CDC.

The director advises that anyone 6 months and older should get at least one updated shot.

"We'd all wish for COVID to be in the rearview mirror but, unfortunately, it's still here," CDC Director Mandy Cohen told ABC News.

The CDC recommended that all Americans aged 6 months and older receive the new COVID booster that targets currently circulating variants.

ABC News' Linsey Davis spoke with new CDC Director Mandy Cohen about the approval of a new COVID booster shot and why she feels it is so important for vaccinated and unvaccinated people to get them.

It comes just a day after the U.S. Food and Drug Administration authorized and approved the new shot.

Despite the continued rise, the most recent week was the smallest percent increase in the past 2 months, according to the CDC data.

The U.S. Food and Drug Administration authorized and approved updated COVID-19 boosters on Monday amid rising cases and hospitalizations. CDC approval is the next step.

COVID-19 hospitalizations are on the rise across the country; nearly 9% over the prior week.

The new shots now await approval from the U.S. Centers for Disease Control before they are available to the public.

The upcoming COVID-19 booster is expected as early as next week.

The updated shot protects against severe disease and death for all current variants, including the now-dominant strain, BA.2.86, the company said.

A new COVID-19 booster from Moderna shows promising results for protecting against a new omicron subvariant, while the CDC reported a rise in RSV cases in the Southeast.

The updated COVID vaccine should be released in mid September.

Over $1.4 billion has been awarded to clinical trials for COVID-19 vaccines, the development of a new monoclonal antibody, and new vaccines and therapeutic technologies.

Despite the rising number of COVID cases and hospitalizations, experts said most people should wait for the updated boosters to be released before getting another shot.

ABC News chief medical correspondent Dr. Jen Ashton explains the recommendations from the FDA to update vaccines against the latest COVID-19 strain, which will likely have mutated by winter.

The study looked at protection offered from the original vaccines but not from the updated bivalent boosters.

A new study found that the original COVID-19 vaccines saw their effectiveness decline against infection with the omicron variant to less than 20%.

An upstate New York midwifery is facing federal charges after allegedly distributing thousands of fake COVID-19 vaccination cards and destroying vaccine vials.

The FDA authorized a second omicron-targeted bivalent COVID-19 booster vaccine for people over 65 or who are immunocompromised.

The agency has withdrawn authorization for the original vaccine and has implemented a strategy similar to the flu vaccine.

Nearly three years after the start of the pandemic, almost all restrictions for COVID-19 safety have been dropped, but some Americans are still worried about their own health.

Here's what the FDA and CDC wrote in a letter to Florida Surgeon General Joseph Ladapo, whose claims about COVID-19 vaccines are "harmful" to public health.

Plus, when you should seek medical attention for a fever, and how to tell if your sugar consumption is too high.

Moderna has announced it will provide its COVID vaccine for free to people without insurance, even after government money dries up.

One of the largest municipal worker COVID-19 vaccine mandates is ending this week as 96% of New York City workers have received their shots, Mayor Eric Adams said.

Roughly 96% of city employees are fully vaccinated, mayor says.

The FDA outlined an approach to yearly COVID vaccines, like the flu shot.

ABC News chief medical correspondent Dr. Jen Ashton breaks down a new study by the CDC on the booster shot’s effectiveness.

According to briefing documents, the FDA is proposing a new COVID vaccine strategy: that most Americans receive one shot per year, similar to the flu vaccine.

More than one year after COVID-19 vaccines authorized for elementary school-aged children, a mountain of data supports they are safe and effective.

The agency's independent advisers are likely to weigh in on guidance that could simplify public health messaging on when to get COVID vaccines and increase vaccination rates.

A group of FDA advisers are meeting Thursday to discuss the new recommendation.

The agency will meet Thursday to discuss offering one updated shot a year for everyone whether they’ve been vaccinated or not.

A plastic surgeon, his neighbor and two of his employees are alleged to have ran a fake vaccination records scheme through the doctor's Salt Lake City-area practice.

The FDA and CDC said that after an investigation, there is no increased safety risk of stroke in people 65 and older who got the updated bivalent Pfizer COVID vaccine. Dr. Jen Ashton explains.