Washington(CNN) Months into the coronavirus pandemic, much about the disease remains unknown. As several countries attempt to regain a sense of normalcy despite recent surges in cases, politicians and scientists alike are working to better understand how the virus spreads and how best to prevent future outbreaks.
At the core of these efforts are a few critical questions: Can children transmit the virus? If you get the virus, how long are you contagious? Afterwards, are you immune or can you get re-infected?
The answers to these questions will influence not only how countries reopen schools and offices but also have implications for how useful any eventual vaccine will be.
Animating the debate on one particular point are some comments that Kentucky Republican Sen. Rand Paul made in a July interview in which he claimed that he, along with millions of others, are now immune from the coronavirus because they had already been infected. Back in March, Paul became the first US senator to test positive for the virus. Paul is a medical doctor and trained ophthalmologist.
While discussing who would likely get a vaccine when one is available, Paul said that "there's millions of us like me now who are immune -- are they going to hold me down and stick a needle in my arm?"
Earlier, Paul also claimed that "since we don't have a vaccine, the one way we get immunity is by having more people get it, and I don't think it could be said enough what a positive thing it is to have millions of people who now have immunity because they essentially are now blocking the spread of the virus."
Facts First: It remains unclear if those already infected with the virus are immune to any reinfection. Additionally, it's unknown how long any sort of immunity would last.
It's currently impossible to know from an antibody test whether someone is immune to the coronavirus, according to Dr. Celine Gounder, an epidemiologist and clinical assistant professor at New York University.
"All you can say from an antibody test is that somebody has been exposed," Gounder told CNN. "You can't really say anything about immunity."
In April, the World Health Organization warned against the creation of immunity passports suggested by some governments, noting that "no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans."
Aubree Gordon, associate professor of epidemiology at the University of Michigan, told CNN the issue with Paul's claim is that "we really don't know."
"Yes, the grand majority of people that have had Covid-19 do develop an antibody response," Gordon said. "However, although the scientific community is generally optimistic, we do not know whether people that have been infected and recovered are generally 'immune' to infection or whether they can be reinfected."
During a briefing in late April, the Infectious Diseases Society of America warned that those previously infected shouldn't assume they have immunity from the virus.
"We do not know whether or not patients who have these antibodies are still at risk of reinfection with Covid-19," said Dr. Mary Hayden, spokesperson for IDSA and chief of the Division of Infectious Diseases at Rush University Medical Center. "At this point, I think we have to assume that they could be at risk of reinfection."
"We don't know even if the antibodies are protective, what degree of protection they provide -- so it could be complete, it could be partial -- or how long the antibodies last," Hayden added.
As Hayden noted, it remains unclear how long antibodies that might be effective against the virus stick around.
Researchers at King's College London found evidence that immunity wanes after just a few weeks. Their study, published on a preprint server and not yet peer-reviewed, supports studies done by the government in Spain that indicate people lose antibodies against the virus after a few weeks.
Gounder also told CNN that medical experts are unsure how long neutralizing antibodies generated by the immune system in response to the coronavirus last.
Dr. William Schaffner, professor of infectious diseases at Vanderbilt University, pushed back on Sen. Paul's claim that the millions of people who have been infected by the virus are now essentially blocking its spread.
"Since we don't know how long natural protection will last, it may be the case that even people who have been infected may require the vaccine at some point," Schaffner told CNN. "That remains to be determined."
He added, "Waiting for the virus to 'immunize' the population is a very Darwinian concept, survival of the fittest. We generally try to avoid that in public health."
Additionally, according to the Centers for Disease Control and Prevention, an uncertain but not negligible percentage of those infected by the virus are asymptomatic and there is some evidence, including a June study of 37 asymptomatic patients, that people without symptoms develop a weaker immune response to coronavirus infection than those who feel sick.