What are booster shots and why might they be key to fighting COVID-19?

It may not be too much longer before Americans are encouraged to get a third COVID-19 booster shot. 

The federal government has given emergency authorization to administer the shots to those with a suppressed or compromised immune system. Both Pfizer and Moderna have also requested approval for the shots to be made eligible to all Americans that have completed their respective 2-series shots.

And on Monday, two people familiar with deliberations within the Food and Drug Administration told the Associated Press the agency was considering broadening who could get the third shot. 

So far, Detroit has already rolled out its own booster shot initiative for some of its residents with preconditions that may make it harder for them to fend off the virus even with the vaccine's protection. It started accepting recipients at the TCF Center on Tuesday for a third shot.

But with just over half of all Americans and 42% of Detroit fully vaccinated, the hesitancy of the original vaccines may track along with promotions of the booster shot.

Here's what we know about a potential third dosage.

What is a booster shot?

An extra dose from a vaccine is not a new phenomenon. It's essentially an extra boost for the body's immune system that might see its protection against a virus wane in the months after completing an initial series. 

From Chickenpox to measles, to tetanus, these are all vaccines that come with extra doses to help children increase the presence of antibodies available to ward off infection. 

Why might we need a booster shot against COVID-19?

It was only nine months ago at the end of 2020 when the government first gave approval for the COVID-19 vaccines, which may feel like only a short time has passed before talk of adding a third dose onto the vaccine regiment. 

But like much of the past year, both residents and health experts have spent a lot of time learning and understanding the new threat to public health. Among the uncertainties still being navigated is the length of time the vaccines offer immunity from COVID-19. 

Countries are still rolling out vaccinations, so it's to be determined just how long protection will last from the Pfizer and Moderna shots. However, preliminary studies have found that protection after a second shot remains high for six months. 

Based on Moderna and Pfizer's request for a booster shot approval, there may be new data suggesting the necessary antibodies fall in their concentration soon after. But that's to be determined, says Beaumont's chief infectious disease doctor.

"Now they're talking about boosters for everybody, and that's based on data we haven't seen yet," said Dr. Matthew Sims. "According to the latest that I've heard, this (booster shots) has been formally submitted to the FDA by both Pfizer and Moderna. Their data at 8 or 9 months suggesting that protection may be waning and a boost might restore and perhaps even improving protection gave after the second dose."

Who is eligible?

While vaccine protection has been shown to be very effective at reducing severe health outcomes, some people with the weakest immune systems may still struggle to fight off an infection.

After the FDA said a third shot could help those groups, the CDC debated Friday before unanimously agreeing that a narrow band of Americans - about 2.7% of the population - could benefit from the shot. 

Those include people who recently received an organ transplant or take medication that suppresses their immune system. 

This guidance pertains specifically to those who already received the Pfizer and Moderna vaccines - and not the Johnson & Johnson vaccine, which has not been studied among the immunocompromised.

The CDC also recommended people try to stick to the same vaccine they received if they plan to get a third shot. 

When will I be eligible?

The Biden administration is expected to recommend booster shots for Americans of all ages in the coming days or weeks. 

The recommendation will be for people eight months after completing their two-shot series.

They could begin as soon as September. 

That Israel Ministry of Health study

Among the pieces of data that are public are the climbing infections rates in Israel, which has one of the highest vaccine rates in the world. 

A big chunk of the new vaccinations in Israel is among vaccinated individuals. While a higher rate of protection would obviously yield more breakthrough infections - those that have been vaccinated but still test positive for a virus - the pace of newly infected people are forcing the third-shot subject into the global health conversation. 

The results show that immunity may be waning among those that got the shot first. People vaccinated in January had a 2.26 times greater risk for a breakthrough infection than those vaccinated in April, according to a study published by the Israel Ministry of Health.