Could COVID-19 immunity last decades? Here’s the science.

The body builds a protective fleet of immune cells when infected with COVID-19, and in many people, those defenses linger for more than six months after the infection clears, according to a new study.

The immune cells appear so stable, in fact, that immunity to the virus may last at least several years, the study authors said. “That amount of [immune] memory would likely prevent the vast majority of people from getting hospitalized disease, severe disease, for many years,” co-author Shane Crotty, a virologist at the La Jolla Institute of Immunology in California, told The New York Times, which first reported on the study.

That said, making predictions about how long immunity to the coronavirus lasts can be “tricky,” Nicolas Vabret, an assistant professor of medicine at the Mount Sinai Icahn School of Medicine, who was not involved in the study, told Live Science.

“It would be surprising to see the … immune cells build up in patients over six months and suddenly crash after one year,” Vabret said in an email. But “the only way to know whether SARS-CoV-2 immunity will last decades is to study the patients over the same period of time.” 

In other words, we won’t know exactly how long immunity lasts without continuing to study those who have recovered from COVID-19. However, the new study, posted Nov. 16 to the preprint database bioRxiv, does provide strong hints that the protection is long-lived — although clearly not in all people, as there have been several cases of individuals being reinfected with the coronavirus after recovering. 

The research dives into the ranks of the human immune system, assessing how different lines of defense change after a COVID-19 infection. 

These defenses include antibodies, which bind to the virus and either summon immune cells to destroy the bug or neutralize it themselves. Memory B cells, a kind of white blood cell, “remember” the virus after an infection clears and help quickly raise the body’s defenses, should the body be reexposed. Memory T cells, another kind of white blood cell, also learn to recognize the coronavirus and dispose of infected cells. Specifically, the authors looked at T cells called CD8+ and CD4+ cells.

The authors assessed all these immune cells and antibodies in 185 people who had recovered from COVID-19. A small number of participants never developed symptoms of the illness, but most experienced mild infections that did not require hospitalization. And 7% of the participants were hospitalized for severe disease. 

The majority of participants provided one blood sample, sometime between six days and eight months after the onset of their infections. Thirty-eight participants gave several blood samples between those time points, allowing the authors to track their immune response through time.

Ultimately, “one could argue that what they found is not so surprising, as the immune response dynamics they measure look like what you would expect from functioning immune systems,” Vabret said. 

The authors found that antibodies specific to the spike protein — a structure on the surface of the virus — remain stable for months and begin to wane about six to eight months after infection. At five months post-infection, nearly all the participants still carried antibodies. The volume of these antibodies differed widely between people, though, with an up to 200-fold difference between individuals. Antibody counts normally fall after an acute infection, Vabret noted, so the modest drop-off at six to eight months came as no surprise.

By comparison, memory T and B cells that recognize the virus appear extremely stable, the authors noted. “Essentially no decay of … memory B cells was observed between days 50 and 240,” or eight months later, Marc Jenkins, an immunologist at the University of Minnesota Medical School, who was not involved in the study, said in an email.

“Although some decay of memory T cells was observed, the decay was very slow and may flatten out at some point,” Jenkins added. There’s reason to believe that the number of memory T cells may stabilize sometime after infection, because T cells against a related coronavirus, SARS-CoV, have been found in recovered patients up to 17 years later, according to a study published July 15 in the journal Nature

Early in the pandemic, scientists raised concerns that immunity to the virus may wear off in about a year; this trend can be seen with the four coronaviruses that cause the common cold, Live Science previously reported. However, studies suggest that the body’s reaction to common coronaviruses may differ from that to viruses like SAR-CoV and SARS-CoV-2, which hopped from animals to humans. 

“We don’t really know why seasonal coronaviruses do not induce lasting protective immunity,” Vabret said. But the new study, along with other recent evidence, suggests that SARS-CoV-2 immunity may be more robust, said Jason Cyster, a professor of microbiology and immunology at the University of California, San Francisco, who was not involved in the study.

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That said, a few participants in the new study did not mount long-lasting immune responses to the novel virus. Their transient responses may come down to differences in how much virus they were initially exposed to, or genetics may explain the difference, Cyster said. For instance, genes known as human leukocyte antigen (HLA) genes differ widely between individuals and help alert the immune system to foreign invaders, Live Science previously reported

These inherent differences between people may help explain cases of COVID-19 reinfection, which have been relatively rare but are increasing in number, Science Magazine reported.

Again, to really understand how long COVID-19 immunity lasts, scientists need to continue to study recovered patients. “Certainly, we need to look six months down the road,” and see whether the T and B cell counts remain high, Cyster said.

Should immunity be long-term, one big question is whether that durability carries over to vaccines. But natural immunity and vaccine-generated immunity cannot be directly compared, Vabret noted. 

“The mechanisms by which vaccines induce immunity are not necessarily the same as the ones resulting from natural infection,” Vabret said. “So the immune protection resulting from a vaccine could last longer or shorter than the one resulting from natural infection.”

For example, the Pfizer and Moderna vaccines use a molecular messenger called mRNA to train the body to recognize and attack the coronavirus. No mRNA-based vaccine has ever been approved before, so “we practically know nothing about the durability of those responses,” Cyster said.

“I think [that’s] the big unknown for me, among the many,” he said.

But while some unanswered questions remain, the main takeaway from the new study is that “immune memory to SARS-CoV-2 is very stable,” Jenkins said. And — fingers crossed — perhaps those hopeful results will hold well into the future.

Originally published on Live Science. 

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These Fruits and Veggies Could Last Months When Stored The Right Way

Any smart shopper would want their fresh produce to last as long as possible. If it doesn’t go bad fast, it means you can save more money because fresh fruits and vegetables can be pretty expensive. Having to throw away rotten ones and restock again can hurt your food budget and is also wasteful.

According to the Environmental Protection Agency, around 94% of food thrown away end up in landfills. This could be lessened just by knowing the right way to purchase, store, and prepare your fruits and vegetables so they will last for as long as possible. But you can also opt to stock up on these products that could last for longer than you would expect, as long as you store and use them correctly.

Potatoes

It’s ideal to store potatoes in 40 degrees Fahrenheit. These veggies don’t like light, so the perfect storage conditions for potatoes is in the basement or a cellar. Light can also make them turn green.

Storing potatoes in this condition keeps them from rotting for around 2 to 4 months. However, keep them away from apples and onions as both of these food items emit gases that could make potatoes ripen faster.

Cabbage

Although cabbage tastes best when it’s fresh, it can also last for up to 2 months if you plan to stock up on it. However, it should be placed inside the fridge and wrapped in plastic. Since cabbages can last longer than lettuce or other delicate leafy greens, it can be used as a stand-in as an ingredient of your salads. Most greens that are frequently used in salads wilt in a matter of days because of their high water content.

Cabbages can be alternatives to salad greens that wilt quickly.

Apples

According to the University of Maine, no other tree fruit could last longer than apples and pears. Under the right conditions, these could last up to 4 months. Apples could thrive in a storage temperature of around 32 degrees Fahrenheit, except for the Honeycrisp variant that should be stored at 36 degrees Fahrenheit because it tends to get a chilling injury.

Among your bunch of apples, consume the largest one first since these are usually the first ones to go bad. Store apples inside a plastic bag and stow it inside the fruit crisper drawer of your refrigerator to prolong it for weeks. Just make sure that you keep them away from veggies. Other vegetables ripen faster when exposed to ethylene gas, which apples emit.

Beets

Beets can be used in a variety of ways. You can slice them up for salads or snack on baked beet chips. It’s a good thing that these veggies can last between 2 to 4 months in your refrigerator if stored properly. If there are still greens attached to the beets, make sure to remove them. After that, place it in a perforated plastic bag and inside the vegetable crisper.

Garlic

These kitchen staples can last the longest when stored at around 60 to 65 degrees Fahrenheit. These should be okay to store inside a dark kitchen cabinet.

A whole bulb could last for months stored inside a paper bag in the fridge. However, all your other food items might taste like garlic if you store them with already cut ones. Once you refrigerate the garlic bulb, you should keep it inside until you are about to use it. Days after it has been taken out from the cold and into room temperature, it will start sprouting.

You should only store unopened bulbs inside the fridge and not sliced ones if you don’t want other food items to acquire a garlicky taste.

Carrots

Carrots give off plenty of moisture, so you have to keep them dry if you intend to use it much later. This is because the moisture makes the carrots rot quicker. If they came in a plastic bag when you bought them from the grocery store, just put in a paper towel inside so it can absorb any moisture from the carrots. Once the paper towel gets saturated, replace it with a new one so you can keep your carrots fresh for up to a few months.

Onions

Onions can last up to a year as long as these are stored in a dry area with a temperature between 30 to 50 degrees Fahrenheit. If you don’t have the proper storage place, just keep it in mesh bags, like the ones used to pack onions sold by the grocery stores. If you store them inside a dark cabinet, they can last to a month or even longer.

Winter Radish

The white-colored daikon variety you see in your local grocery store is more pungent than the red ones you use for spring salads. So, if you’re looking for a healthy supply of fresh produce, don’t store too many of these. Storage for winter radishes is similar to that of carrots. After you remove the greens, place the radishes inside a plastic bag with a paper towel to absorb moisture. That way, these could last for about a month.

You can use shredded or thinly shaved winter radish for your slaw or salad.

Winter Squash

Varieties of winter squash, including pumpkins and butternut squash, can last around 2 to 6 months if stored inside a dark cabinet. Just make sure that you arrange them in a single layer so that air can circulate better. Stocking up on these versatile vegetables is a smart choice since these are packed with nutrients and can be used in a number of recipes.

Frozen Vegetables

Aside from your fresh produce, also hit the frozen foods aisle and stock up on a couple of packs of frozen vegetables. It may be healthier than fresh asparagus, spinach, peas, and other veggies with a short shelf life as these were frozen just hours after being harvested. Plus, you don’t have to worry too much about expiration as long as you keep it inside your freezer.

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