"We are continuing to learn a year into the pandemic," Dr. Becky Smith, medical director of infection prevention and control and an infectious diseases specialist at Duke University Hospital, told CNN in an email.
Yet there are still some answers to questions that doctors say Covid-19 survivors should know.
How much of a risk is reinfection?
The risk of reinfection "seems to be quite low" and the US Centers for Disease Control and Prevention "states the risk of reinfection is 'low' within the first 90 days of having a Covid infection," Smith said. Although rare, the risk exists.
"Based on what we know from similar viruses, some reinfections are expected," the CDC notes on its website.
"The risk of reinfection remains low, but we have to be vigilant with the emergence of the new variants," Dr. Antonio Crespo, medical director of infectious diseases at the Orlando Health Medical Group Infectious Disease, told CNN.
The novel coronavirus that causes Covid-19 has changed over time, as all viruses do, and through these mutations, variants of the virus have emerged.
Scientists are not surprised to see the coronavirus changing and evolving -- it's what viruses do, after all. And with so much unchecked spread across the United States and other parts of the world, the virus is getting plenty of opportunity to do just that.
So far, three variants circulating around the world have been identified and getting a lot of attention: variant B.1.1.7 was first identified in the United Kingdom, variant B.1.351 was first identified in South Africa and variant P.1 was first identified in Brazil.
The coronavirus variants circulating globally are projected to become more dominant in the United States by the spring, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a White House news briefing last week.
At the same briefing, CDC Director Dr. Rochelle Walensky said that every Covid-19 case in the United States now should be treated as if it is caused by one of the newly identified coronavirus variants.
Another reason why the risk of reinfection remains somewhat a mystery is because it remains unclear for just how long Covid-19 antibodies might last in your body.
How long will my antibodies last?
Antibodies are proteins your body makes soon after you've been infected. They help to fight the infection and can protect you from getting that disease again.
"What we know is that when somebody gets infected with Covid-19, they do get antibodies that can last," Crespo said. "But now the new science that is emerging is that some of the coronavirus variants could evade the antibodies and could potentially be infectious for somebody who had already been infected with a well-known variant of Covid-19."
Smith said that in one large study of more than 12,000 health care workers at Oxford University Hospitals in the United Kingdom, very few with Covid-19 antibodies became infected a second time during a six-month period. That study, published in the New England Journal of Medicine in December, suggests that antibodies are associated with "a substantially lower risk of reinfection."
"Those who developed reinfection had asymptomatic infections," Smith said in her email. Smith added that anecdotal evidence from her hospital's experience in managing Covid-infected health care workers suggests that antibodies are likely protective against reinfection.
"To date, approximately 0.5% of health care workers have experienced reinfection events, though we acknowledge have not systematically checked for Covid antibodies as in the Oxford study," said Smith, who was not involved in the study.
People who have been infected with Covid-19 are likely to be protected against catching it again for at least five months, according to a new study led by Public Health England.
The study -- which has not yet been peer reviewed -- found that past infection was linked to an 83% lower risk of reinfection, compared to people who have not been infected before.
But researchers warned that the protection was not absolute, meaning some people do catch the virus again, and that it was unclear how long any immunity lasts. It is also possible that those who have a degree of immunity against the virus may still be able to carry the virus in their nose or throat and therefore transmit it to others.
Do I need to get the vaccine if I've had Covid-19?
Health officials and doctors encourage people who have had Covid-19 to still get vaccinated. Late stage clinical trial data suggested the vaccines are safe and helped protect people with past Covid-19 infections from reinfection. This was regardless of their past case being mild or severe.
"Even if someone had a natural Covid-19, my recommendation is to get vaccinated as soon as vaccine is available to you," Smith said.
"It is very clear that the two available vaccines afford a high level of protection as measured in neutralizing antibody titers. This may be particularly important for people who had an asymptomatic or mild infection," she said. "Having a higher level of antibody titers to begin with will protect you for a longer amount of time."
Smith added that the Pfizer/BioNTech and Moderna vaccines, authorized for emergency use in the United States, appear to provide some protection against the emerging coronavirus variants circulating around the world.
"We are not sure if natural immunity will protect someone from getting infected with the new strains," Smith said.
A person who is currently sick with Covid-19 should, however, wait to get the vaccine after their symptoms have cleared up and they can come out of isolation. There's no recommended minimum time between infection and vaccination.
Also there is no safety data on people who have been given an antibody therapy or convalescent plasma to treat a Covid-19 infection. Since reinfection seems to be uncommon in the 90 days after the initial infection, as a precaution, the CDC recommends the person wait at least 90 days.
There's no data that shows a vaccine would protect someone who has been recently exposed. A person isn't fully protected until one or two weeks after they get the second dose of the vaccine.
Do I need both doses of the vaccine?
The Pfizer/BioNTech and Moderna vaccines authorized for emergency use in the United States are administered in two doses, 21 and 28 days apart, respectively.
It's currently recommended for people to follow that vaccine schedule until more research is conducted and health officials recommend otherwise.
"The concept of giving just one booster vaccine to those who have had natural infection has been raised as a way to preserve the limited supply of vaccine and make it available to those who never developed Covid infection," Smith said.
Some emerging evidence in a pre-print paper, posted to the online server medrxiv.org on Monday, found that after getting just one shot of a Covid-19 vaccine, people who were previously infected with the virus tended to have antibody levels that were at or above those of people who had gotten both doses but never been previously infected. The study does not specify which vaccine participants received.
"Logically, people who have had Covid infection are likely to start with a baseline of some detectable neutralizing antibody so you are not starting from scratch like you would be for individuals who never had Covid," Smith said.
"However, the amount of neutralizing antibodies decreases over time so this needs to be carefully studied before rolling it out," she said. "We would need data to determine the optimal timing of the booster from natural infection and whether the duration of protection is equivalent to the protection you get from two doses of vaccine."
Smith added that coronavirus variants would also remain a risk.
"We also are unsure about variant strains and how well antibodies developed from natural infection protect someone against a new strain. Vaccines have been tested and afford protection based on limited data," Smith said. "Finally, this approach would require patients to get antibody tested before vaccination and this may not be readily available for everyone."
Could I still be experiencing lingering effects Covid-19?
Many survivors of Covid-19 may experience symptoms for weeks or months.
"Patients may experience persistent severe fatigue, headaches, 'brain fog,' mild cognitive impairment/difficulty thinking or concentrating, joint pains, cough, shortness of breath, intermittent fevers, alterations in taste and smell among other symptoms," Smith said. "These lingering symptoms may last up to 12 weeks and many say the symptoms wax and wane or come and go during that time."
Whether you suffer lasting Covid-19 symptoms may depend on the severity of the disease that you have.
"Some people have mild symptoms and they recover quickly and they don't have major problems. One of the side effects that we've seen very often is chronic fatigue," Crespo said.
"It seems that with patients with Covid-19, it's one of the common symptoms that can linger for several months," he added. "Also if patients have had significant lung involvement with severe pneumonia, they may have difficulty recovering from that persistent shortness of breath, cough and getting easily tired."
Crespo added that, even if you have lingering effects, it's still important to get the Covid-19 vaccine when it is your turn.
"They should get the vaccine," he said. "I don't see that having lingering effects would have a particular effect on the response to the vaccine."
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