EVANSTON, IL — Is it possible you were infected with a mild form of COVID-19 and didn’t know it? How robust is your body’s immune response to the vaccine, and how will we know whether we’ve reached herd immunity? A new home antibody test could unlock the answers to those questions using a drop of blood.

With a single finger prick, scientists are hoping to measure coronavirus immunity levels across the population.

“There are a lot of people right now, because of limited vaccine supply, who don't know the level of immunity that they have,” explained biological anthropologist Thom McDade.

McDade and a team of scientists at Northwestern University developed the home antibody test that doesn’t require a hospital or clinic visit.

“One of the innovations of this approach is that allows people to collect samples from themselves in the comfort and privacy and safety of their home,” he said.

This test doesn’t tell you if you have COVID-19 when you take it. Instead, it focuses on neutralizing antibodies, which can actually measure how robust of an immune response you actually have following an infection.

“If you've been exposed previously, but might have had a mild or asymptomatic case, how much immunity do you carry forward and how much protection you have against subsequent re-infection from another exposure?”

The test itself is simple. A few drops of blood are added to a commonly used filter paper then sealed in a plastic bag and mailed off to the lab. There, the sample is mixed with a buffer agent that replicates infection and measures neutralization of the virus with a score of 1 to 100.

“If you have 100 percent neutralization that means high levels of neutralizing antibodies that are blocking that interaction between the virus and your receptors,” said McDade.

The investigators are already using the test in a 10,000-person study. That could help them understand community spread and how much protective immunity has developed.

“That could be people who have never exposed people who are exposed and asymptomatic and we can also use it to test the effectiveness of vaccines,” said McDade. “There might be people who have immunocompromised condition or who are older who might not generate as robust an immune response following vaccination and that would be useful information.”

With nothing proprietary about the process, following peer review, McDade said it could be made widely available with existing infrastructure and supplies and could help measure herd immunity.

It’s still not clear whether this test can measure the effectiveness of neutralizing antibodies against emerging variants, but researchers say it could be modified for specific variants as needed.

Sixty-two percent of Americans say they have either received a COVID-19 vaccine or are seeking one as soon as possible, according to a poll released Tuesday by the Kaiser Family Foundation (KFF).

Since December, the poll has found more Americans are eager to get vaccinated. In December, just 34% said they were seeking a vaccine as soon as possible. In January, the number was up to 47%, and last month, 55% said they would get vaccinated as soon as possible.

The March 2021 poll found that 17% would wait and see, which is down significantly from past polls.

Roughly one-fifth of those polled said they would definitely not get a vaccine or only get one if required, which is consistent with recent polls.

The KFF poll also found that one-third of Americans who say they’re eligible for a vaccine have attempted to schedule a shot, but nearly half of them have been unsuccessful.

As of Tuesday, 28.9% of the US population is partially or fully vaccinated, and 16.1% are fully vaccinated, according to a CDC database.

How many Americans needing to be vaccinated to achieve herd immunity is a question scientists are still trying to grapple with. The threshold for herd immunity varies based on the transmissibility of a disease. For instance, measles requires 95% vaccination rates to achieve herd immunity, according to the World Health Organization, however for a disease like polio, only 80% need to be vaccinated for herd immunity.

COVID-19 vaccine providers and local health officials are concerned about the drop in demand for the shots, as mask rules relax throughout the Tri-State region.

"If we don't step up and get vaccinated, or if certain sectors of communities don't get vaccinated, the virus can run rampant in those sectors," said Suzi Francis, ambulatory clinical pharmacy manager at St. Elizabeth's Hospital.

In Northern Kentucky, less than one third of the population is fully vaccinated. Ohio counties range from 21% to 42%.

Clinics open to walk-ins remain busy, but there are signs that demand is trailing off.

"We are filling our appointments, but it is taking a little bit longer," said Francis. "I think we're to the population that hasn't seen as much of the personal devastation that COVID could cause or they feel like they're safer because they're younger."

People in their 20s have more active COVID-19 cases than any other age group in Northern Kentucky, Ohio and Indiana.

As schools and universities approach summer break and mask restrictions and capacity limits relax region-wide, health officials worry that more contagious or severe variants of the virus could become an issue in unvaccinated groups.

"I think this is important, when you make that decision, when you're thinking your hesitancy, saying 'well I made it this far, I might as well not bother with it,'" said Dr. Carl Fichtenbaum, professor of infectious diseases at UC College of Medicine. "That would be true if the virus wasn't changing. But with the virus changing and adapting to its environment, you have to change and adapt too."

Until herd immunity is achieved, health officials expect virus mutations to continue increasing the likelihood of necessary booster shots for those who have already been vaccinated.

Nearly a third of all Americans are fully vaccinated against the coronavirus.

It's why many states have recently announced new timelines to fully reopen.

Data from the Centers for Disease Control and Prevention (CDC) shows more than 56% of U.S. adults have received at least one dose of the COVID-19 vaccine.

In order to reach herd immunity, health leaders say that number needs to be around 70 to 85%. 

But some experts worry the demand may not be there. 

"What I really worry about is that those people who are already on the fence don't get vaccinated, we don't reach herd immunity come the fall, and in the winter, because coronaviruses are a big respiratory viruses we have a big resurgence, maybe we have variants coming in from other countries," said Dr. Leana Wen.

Doctors are worried younger adults aren't getting vaccinated. A Quinnipiac University poll found that 36% of adults under the age of 35 say they don't plan to get a shot.

This story was originally published by Robin Dich and Alex Livingston at Newsy.