aamc.org does not support this web browser.
  • AAMCNews

    Had COVID recently? Here’s what to know about how long immunity lasts, long COVID, and more

    Four years after the emergence of SARS-CoV-2, experts know more about mutating strains, vaccine effectiveness, and long COVID. Here's what it means for you.

    Close-up of adult hand holding a positive result COVID-19 or SARS CoV-2 test kit with result

    More than four years after the emergence of SARS-CoV-2, most people are eager to leave COVID-19 in the rearview mirror.

    Unfortunately, the virus has far from disappeared.

    In the last week of December 2023 and the first few weeks of January 2024, the United States saw a bump in COVID-19 infections and hospitalizations, according to the Centers for Disease Control and Prevention (CDC) COVID Data Tracker. Deaths caused by the virus have hovered around 1,400 per week since September 2023 and peaked at 2,029 weekly in early January, bringing the total COVID-19 deaths in the United States to 1.17 million by the end of January 2024.

    These numbers are far lower than the hospitalizations and deaths during the peak of the pandemic, when more than 25,000 people in the United States died in a single week in January 2021. Infectious disease experts say this is because the virus has mutated to cause less severe disease, and most people now have some form of immunity between prior infections and vaccine protection.

    Still, as hundreds of millions of people continue to get infected with the virus, and at least 20 million Americans have been diagnosed with long COVID, infectious disease experts warn the public to not let down their guard.

    “There is a little bit of the complacency of people saying, ‘Now SARS-CoV-2 is over, I don’t need to worry about it anymore,’” says Alessandro Sette, Dr. Biol. Sci., co-director of the La Jolla Institute Center for Vaccine Innovation and an adjunct professor at the University of California, School of Medicine La Jolla Institute for Immunology. “That is not true. We are in a new phase.”

    AAMCNews spoke with experts from academic medical institutions specializing in immunology, vaccinology, epidemiology, and critical care to answer common questions about COVID-19 in 2024.

    How is the JN.1 variant different from previous strains?

    The JN.1 variant, which is a subvariant of omicron, accounted for 83%-88% of all currently circulating variants of SARS-CoV-2 as of Jan. 19, according to the CDC. The subvariant is known among virologists as a “hypermutated variant,” Sette says.

    “That is potentially concerning in the sense that it’s associated with potential for escaping the neutralizing antibody response,” notes Sette.

    This could explain an increase in people getting symptomatic disease, even after having been vaccinated or previously infected. Still, evidence suggests that this variant does not cause more severe disease than other variants. And T-cells, the body’s second line of defense against foreign pathogens on a cellular level, continue to respond well to infections with JN.1, Sette and a cohort of scientists in Sweden found in a recent study. Another study that is currently in preprint found that the body’s immune system can adapt to recognize the virus, even with various mutations.

    “So that is huge, potentially,” Sette says. “The immune system can actually keep up as the virus keeps mutating.”

    This is good news for people with healthy immune systems, and especially for those who get vaccinated, since it means they will likely be able to fight off the virus more easily.

    How long does immunity from a COVID-19 infection last?

    The immune response from a COVID-19 infection usually tamps down after 3-4 months, says Kawsar Talaat, MD, a vaccinologist and associate professor in the Department of International Health at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins School of Medicine in Baltimore, Maryland.

    If a person was infected during this latest wave and hadn’t gotten the most recent COVID-19 vaccine, Talaat recommends getting vaccinated 3-4 months after recovering from the illness to maximize protection.

    While COVID-19 rates tend to increase during the winter months in the United States, the virus hasn’t yet fallen into a predictable seasonal pattern, with occasional regional surges throughout the year. For now, Talaat recommends that people follow the CDC’s guidelines for vaccination. People at higher risk of complications from the virus might need more frequent vaccines under the advice of their physician.

    “I hear a lot of, ‘COVID isn’t so bad anymore, why should I keep getting vaccines?’” Talaat says. “The reality is COVID isn’t so bad if you’re younger, healthier, and have a normal immune system. People with risk factors are still getting sick, being hospitalized, and, unfortunately, people are still dying.”

    Can I get COVID-19 even if I’m up-to-date on vaccines?

    Yes. Talaat notes that the vaccines that are currently available do not fully protect against infection and mild symptoms, which explains why some people get sick even after being vaccinated, but vaccines are effective at preventing severe disease. Because vaccination primes the immune system to the virus, vaccinated people and people who have been previously infected with the virus are likely to mount a quicker and stronger immune response, which can reduce the viral load in the body and moderate symptoms.

    Those who have received the 2023 updated vaccines are more likely to dodge infections than those who haven’t. The CDC found that recent vaccination with the updated vaccine reduced symptomatic infections by 54% compared to those with waning immunity from an out-of-date vaccination status.

    If I have COVID, should I take Paxlovid?

    The Food and Drug Administration has approved the oral, antiviral medication, Paxlovid, to be prescribed for patients with mild or moderate symptoms of COVID-19 who have at least one risk factor for severe disease, such as people over the age of 50, people with chronic disease, or people with weakened immune systems. It must be taken within five days of the onset of symptoms in order to be fully effective. Studies have found the drug to be very effective at reducing risk of hospitalization and death.

    Some people have reported experiencing a “rebound” after taking Paxlovid, meaning they seem to get better and then test positive again or experience symptoms again after a few days. However, physicians say the drug is still worthwhile for those at risk of severe disease, according to an article published by Yale Medicine, particularly since there’s little evidence Paxlovid is any less effective against the more severe outcomes in these cases.

    Paxlovid may also reduce the risk of developing long COVID, explains Ziyad Al-Aly, MD, FASN, chief of research and development at the Veterans Affairs St. Louis Health Care System and clinical epidemiologist at Washington University in St. Louis, Missouri.

    What are the risks of long COVID? Are there any treatments?

    Al-Aly, who is one of the leading experts studying long COVID, says that people in his field tend to divide long COVID patients into two camps: those whose primary symptoms are brain fog, fatigue, dysautonomia (dysfunction of the autonomic nervous system), and post-exertional malaise; and those whose primary symptoms result from damage to organs.

    “Long COVID can affect nearly every organ system,” Al-Aly says. “It can affect nearly everyone … across the lifespan, across demographic groups … It’s a very heterogeneous disease.”

    The chances of developing long COVID also seem to increase with each infection.

    “We clearly see people who say, ‘I had COVID three years ago, I did just fine. I had it a second time and was just fine,’ only to succumb to long COVID after a third infection,” he says.

    When policymakers and the public only measure the impact of COVID-19 by counting deaths and hospitalizations, they miss the approximately 20 million in the country who have long COVID, including about 4 million people who can’t work due to long COVID symptoms, Al-Aly explains.

    And while Al-Aly and others in the field have conducted significant research into long COVID over the past four years, they are still unable to fully explain its cause or offer a cure or treatment beyond symptom relief.

    Many of the patients who come to the Comprehensive COVID-19 Center (CCC) at Northwestern Medicine in Chicago come with a variety of unexplained symptoms and no diagnosis, adds Marc Sala, MD, a pulmonary and critical care specialist and co-director of the CCC. The CCC brings together a multidisciplinary team that includes specialists in neurology, pulmonology, cardiology, otorhinolaryngology, and other specialties to study and treat the varied symptoms of long COVID.

    “Some of the symptoms are nonspecific, like fatigue and shortness of breath, brain fog and cough 90 days after a COVID infection,” Sala says. “We do a good medical workup to rule out non-COVID causes, then you’re left with diagnosis of exclusion [since] there is no biomarker for it.”

    Sala explains that one leading hypothesis on the cause of long COVID is that the virus hides in the body and continues to stimulate the host immune response over time. As the body is unable to fully clear the virus, patients with long COVID stay in a prolonged inflammatory state. With more research and clinical trials, he’s hopeful that there will be progress on developing treatments.

    But Sala fears that as the public has grown weary of COVID-19, interest — and funding — will move on to other issues, despite its importance.

    “Even if numbers [of long COVID cases] dwindle, there is value in studying this kind of [post-viral] condition,” Sala says. “I don’t think this is the last virus of this nature we’ll see.”

    Do the vaccines work against the latest variants?

    The experts were unanimous on the question of the value of vaccines: they’re underappreciated.

    In the United States, only 21.8% of adults and 11% of children had received the updated COVID-19 vaccine as of Jan. 26, 2024, despite nearly half of adults and children receiving a flu vaccine.

    “I can’t tell you how amazing and unexpected it was that we basically hit a near home run with the first [mRNA] vaccines,” Talaat says. “They’re incredibly effective at saving lives and preventing hospitalizations.”

    She noted that the current vaccines don’t prevent infection, but there are new vaccines in clinical trials that could be delivered nasally that might stop a COVID-19 infection before it starts.

    In the meantime, the existing vaccines can make a huge difference for public health.

    “You should get the vaccine to protect yourself, and if you think you’re healthy, think about getting the vaccine to protect the loved ones around you who are at higher risk of having severe disease,” Talaat says. “None of us live in bubbles; we live in a community.”

    Al-Aly goes further, encouraging people to “mask strategically,” like on public transportation, and by lobbying policymakers to move forward with interventions like requiring buildings to have air filtration systems that reduce the circulation of infectious particles in the air.

    “We need a sustainable research endeavor,” Al-Aly says. “Pandemics produce disability and disease, we must study how [to] treat it, not only for the sake of people who are sick now, but for the sake of our kids and grandkids who are going to experience future pandemics.”