New Evidence That Coronavirus Antibodies Only Last a Few Months

  • New evidence adds to the growing belief that coronavirus antibodies wane rapidly, creating the risk of reinfections.
  • Experts say it’s reasonably clear that immunity from natural infection won’t hold up for years and years but likely dwindle after 2, 3, maybe around 5 months.
  • Because COVID-19 is highly transmissible, our best shot at achieving herd immunity is through an effective vaccine.

A new, large study from the United Kingdom has discovered that protective antibodies against the new coronavirus, SARS-CoV-2, decline rather quickly in people who have recovered from COVID-19.

The research, which was conducted by researchers at the Imperial College London, found that the number of people with detectable antibodies fell by about 26 percent between June and September.

The evidence adds to the growing belief that coronavirus antibodies wane rapidly, creating the risk of reinfections.

“We are pretty sure that just based on the seasonal, regular coronaviruses that cause colds that people can get reinfected over and over again. I was pretty confident that we would not have protective antibodies that would last forever, at least not from natural disease,” said Dr. Yvonne Maldonado, an infectious disease specialist with Stanford Health Care.

Given the data available, it’s reasonably clear that immunity from natural infection won’t hold up for years and years but likely dwindle after 2, 3, maybe around 5 months.

That said, researchers are still uncovering the durability of antibodies after infection, and we’ve yet to record what antibody levels could be like a year after infection.

Either way, because COVID-19 is highly transmissible and life threatening to many, our best shot at achieving herd immunity is through a long lasting, effective vaccine.

Antibodies are thought to wane quickly

More than 350,000 study participants in England took a blood antibody test to help researchers understand how long people with a coronavirus infection have protective antibodies.

The first round of testing included 99,908 participants and took place late June and early July. It found that 60 per 1,000 participants had antibodies.

The most recent round, conducted in September, found that 44 per 1,000 participants tested positive for antibodies, suggesting the number of people with detectable antibodies fell by about 26 percent in just a few months.

The researchers found that the decline in antibodies was most common in older adults over 75 and people who had asymptomatic or mild infections.

Adults who had severe cases — along with healthcare workers, who are likely regularly exposed to the coronavirus — had higher levels of antibodies.

The findings support other recent data that suggest antibody levels against the coronavirus drop quickly.

However, some small studies — like a report from Iceland showing people had antibodies past 4 months — indicate antibodies may last a bit longer.

More research, and time, is needed to pinpoint exactly how long antibodies last in people who’ve recovered from an infection.

Another study from Mount Sinai in New York recently found that people with mild and moderate infections produced a robust antibody response that persisted for 3 months, with a modest dip in antibody levels occurring around the 5-month point.

The Mount Sinai researchers suspect neutralizing antibodies that specifically target the viral spike protein could lower people’s risk for reinfection.

More research is needed to determine how various types of antibodies that target different parts of the coronavirus behave over time.

Breaking down types of antibodies

Maldonado says different types of antibody tests tell us different things about antibodies.

Antibodies come in all shapes and forms, and target different parts of a virus.

Some tests look for general antibodies, which solely indicate whether a person has had an infection, whereas other tests look for specific types of antibodies that confer protection — aka neutralizing antibodies.

Most commercial antibody tests look for general antibodies, whereas the tests included in research studies rely on neutralizing antibody tests (which Maldonado says are the better marker of whether immunity will last).

In addition, though antibodies provide a good picture of what a person’s protection against a virus is like, T cells, which also recognize and target the coronavirus, contribute to a person’s immunity, too.

“T cell immunity, which isn’t always measured, may provide some protection,” said Dr. Onyema Ogbuagu, a Yale Medicine infectious disease specialist.

“That said, real-world experience suggests reinfections are very rare, but would be interesting to see if there is a seasonality to the virus with waning immunity next year,” he said.

What this means for our immunity

Most other coronaviruses, known to cause common colds, have short lasting immunity.

“In general, respiratory viruses don’t produce long lasting immunity or lifelong immunity. You can get those infections over again,” Maldonado said.

But even if antibodies wane over time, there may be some residual immune memory, according to Dr. Ellen Foxman, a pathologist and immunobiologist in the Department of Laboratory Medicine at Yale.

“In other words, regardless of the antibody levels detected when someone is healthy, upon reexposure the immune system still may be able to mount a faster immune response in someone who has recovered from infection than in an individual who has never been exposed,” Foxman said.

Researchers are still evaluating what an antibody response means when it comes to COVID-19 immunity.

Though antibodies generally offer protection, there’s also the chance they could have no effect, or even make a second infection worse, says Foxman.

Health experts suspect immunity will vary from person to person.

People who get sicker have higher levels of antibodies that last longer. Those with asymptomatic infections often don’t have measurable antibodies in their blood.

“The response to the virus is variable from one person to another, and we don’t know why,” Maldonado said.

Why a vaccine is our best bet at herd immunity

To achieve herd immunity, at least 50 to 70 percent of the population needs to have immunity (either from a vaccine or natural infection).

According to Maldonado, we’re not even at 10 percent yet.

With natural infection alone, hundreds of thousands or potentially millions of people would have to die for the population to achieve herd immunity.

“Having a vaccine is the best way to create herd immunity,” Maldonado said.

Additionally, if people’s natural immunity starts to wane, you have new waves of infection, similar to the seasonal flu virus.

Before the vaccine for measles, outbreaks were still common among children, and herd immunity was effectively never reached.

Foxman says vaccines are strategically engineered to produce a strong, robust antibody response that’ll last.

The measles vaccine is the gold standard. Given in two doses, it provides lifetime immunity against the infection.

There’s also the HPV vaccine, which provides higher levels of antibodies than natural infection, notes Maldonado.

We don’t see that with many vaccines; even some degree of protection can go a long way.

“Even if the vaccine doesn’t work 100 percent of the time, and maybe the antibody levels drop over time, if they last long enough and you give the vaccine to enough people, you can actually calculate how long it would take to develop enough herd immunity to stop the virus from circulating,” Maldonado said.

It’s too soon to know how durable a COVID-19 vaccine will be, but if it holds up, it’ll be our best shot at achieving herd immunity.

“The immunity afforded by a vaccine could be better the protection afforded by natural infection — if the vaccine is a good vaccine,” Foxman said.

The bottom line

A new, large study from the United Kingdom has discovered that protective antibodies against the new coronavirus decline rather quickly in people who have recovered from COVID-19.

The evidence adds to the growing belief that coronavirus antibodies wane rapidly, creating the risk of reinfections.

A long lasting, effective vaccine is our best shot at achieving herd immunity, but it’s too soon to know just how durable a COVID-19 vaccine will be.


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