- For those who recover from COVID-19, new research shows immunity to the virus can last for at least 8 months, and may last much longer.
- Understanding how our immune system responds to the virus is an important step in vaccine development.
- Currently two vaccines, from Pfizer-BioNTech and Moderna, are authorized for use in the United States.
- Several other promising vaccines are also in development, but until they become widely available we must practice physical distancing and mask-wearing to keep transmission down.
All data and statistics are based on publicly available data at the time of publication. Some information may be out of date.
Since the start of the COVID-19 pandemic, there’s been a push to develop and roll out a vaccine against the SARS-CoV-2 virus.
If scientists and health professionals can do that quickly, and while we slow the spread of the disease, it’s believed that we can limit deaths by achieving herd immunity.
While scientists have been working hard on many fronts to understand the virus and develop controls for it, there’s still much we don’t know about immunity after recovery from COVID-19, including how long it lasts.
Knowing how long immunity lasts is important in creating vaccination protocols.
According to Lauren Rodda, PhD, a senior postdoctoral fellow in immunology at the University of Washington School of Medicine, we don’t know for certain if people are immune to reinfection simply because not enough studies have been done yet.
“This would require tracking the re-exposure of a significant number of people and determining if they get sick,” she said.
Our knowledge in this area continues to grow, however, as new studies are conducted.
Most recently, a study published in the journal Science has found that immunity can last for as long as 8 months.
According to Shane Crotty, PhD, a professor at the La Jolla Institute of Immunology who co-led the study, his team measured all four components of immune memory:
- memory B cells
- helper T cells
- killer T cells
This is the largest study ever for any acute infection that has measured all four of these components, he said.
The researchers found that these four factors persisted for at least 8 months following infection with the virus.
This is important because this shows that the body can “remember” the SARS-CoV-2 virus. If it encounters the virus again, the memory B cells can quickly gear up and produce antibodies to fight the re-infection.
Those who have recovered from COVID-19 could have immunity against reinfection for months, or perhaps even years, the authors said.
Prior to this latest study, Rodda said that work had been done by her research team, as well as others, showing that antibodies against the virus are maintained for at least 3 months.
In her team’s study in particular, it was shown that this occurs even in people who have mild symptoms.
Their study also suggested that immunity could last much longer.
In a different study published in The New England Journal of Medicine, researchers in Iceland studied 1,107 people who had recovered from COVID-19 and tested positive for the antiviral antibodies.
Over a 4-month period of time, they found that those antiviral antibodies against COVID-19 had not declined.
In addition, a study published in the journal Immunity found that people who recover from even mild cases of COVID-19 produce antibodies that are believed to protect against infection for at least 5 to 7 months, and could last much longer.
Their team has tested nearly 30,000 people in Arizona since they began on April 30, shortly after they developed a blood test for coronavirus.
However, Dr. Steven Sperber, interim chief of the division of infectious diseases at Hackensack University Medical Center, pointed out that there’s still “much” that experts don’t know about SARS-CoV-2 because it’s such a new coronavirus.
He said that among those questions remaining to be answered are:
- Are you protected after infection? How long does the protection last?
- Are there factors related to the patient (such as age) that affect immunity?
- Are there factors related to the virus infection (such as severity of illness) that affect immunity?
- What’s the best way to measure immunity? Is it by measuring antibodies? Is there a specific type of antibody to measure?
- How long will protection last after vaccination?
Sperber further advised that until we do understand more, it’s best to continue to take precautions, such as physical distancing and mask-wearing, even after you recover.
Sperber said that, at this time, we don’t really know if having a positive antibody test means that you’re immune to the virus.
The presence of antibodies only means that you’ve been exposed in the past.
Sperber explained that, for some infections, antibodies may provide protection against reinfection.
For others, they may not prevent reinfection, but symptoms may be milder.
In yet other cases, antibodies may provide no protection at all.
In addition, some test results may be “false positives”: A person may have been exposed to a similar virus that’s also detected by the test, but these antibodies aren’t protective from the new coronavirus.
Finally, he said, we don’t know at this point how long any protection achieved might last.
According to Rodda, “herd immunity is the concept that if enough people are protected from infection, either by gaining immunity from having the infection or receiving a vaccine, then the chance of a nonimmune person contracting the disease is exceedingly low.”
“This is important because there are people in our communities (babies, the elderly, people who have weakened immune systems) that cannot get immunized and they must rely on the rest of us taking precautions to protect them,” she said.
However, Rodda added, it would be a bad idea to simply allow the disease to spread unchecked in an effort to reach herd immunity more quickly.
“COVID-19 can be fatal in any age group,” she said, “and the cost to human life is appallingly unacceptable.”
A vaccine is the ideal way to achieve herd immunity, according to Rodda.
Sperber agreed with Rodda that a vaccine is the best path forward, adding that widespread use of vaccines is key.
“Underutilization of effective vaccines can prevent the development of herd immunity and result in continued spread of infection,” he said.
Experts say the best way forward with COVID-19 is to develop and roll out an effective vaccine against the SARS-CoV-2 virus.
A vaccine will help us control the virus by creating herd immunity.
Understanding how our immune system responds to the virus is an important step in vaccine development.
While there’s much we don’t know yet, it appears we may develop immunity to the virus for at least 8 months.
Currently, there are
Several other promising vaccines are in development, but until they’re available, we must practice precautions like physical distancing and mask-wearing to keep transmission down.