Sadly, vaccines cannot prevent every single illness — and the same is true for current COVID-19 vaccines, as officials at the Centers for Disease Control have begun sharing more details of what are known as 'breakthrough' coronavirus cases. Because SARS-CoV-2, the virus that spreads COVID-19 around the world, has mutated and developed into different viral strains over time, fully vaccinated individuals may become infected and not immediately know it. These breakthrough cases are mounting as CDC officials have reported 6,000+ individuals being treated for their illnesses nationwide, even though that figure may be underreported.
What is a 'breakthrough' COVID-19 case?
The rise in breakthrough cases may be traced back to a version of the virus now classified as the Delta variant, which may be even more contagious among Americans currently than viruses that lead to MERS, Ebola, the flu or the common cold, according to CDC documents acquired by the New York Times. The Delta variant is proving to be much more contagious than previous iterations of SARS-CoV-2, as this strain had triggered more than 80% of all new COVID-19 cases here in the United States by mid-July, per CDC estimates.
While it's certainly more contagious, COVID-19 breakthrough cases prompted by the Delta variant won't result in new symptoms that experts have never seen, explains Marisa Montecalvo, M.D., an infectious disease specialist at New York Medical College. Many of the same symptoms that have been challenging for healthcare providers to treat over the course of the pandemic are still associated with the Delta variant and with breakthrough cases so far.
Even if you are among those who experience a breakthrough infection, vaccinated individuals are much less likely to have severe symptoms when it comes to respiratory issues, fevers, aches or gastrointestinal pains. It's why it can be confusing for most vaccinated individuals to differentiate a potential cold or stomach bug from a breakthrough COVID-19 infection — symptoms are usually much milder than for those who are unvaccinated.
Whether you've been fully vaccinated for a few months' time or are still building immunity after your first shot, keeping the following symptoms in mind can help you determine if it's worth seeking out a COVID-19 test or immediate medical attention.
What are the symptoms of a breakthrough COVID-19 infection?
Regardless of which strain may be impacting your health (Delta or otherwise!), it's important to remember that a COVID-19 sickness looks and feels different for everyone — there isn't only one set of symptoms that could impact you if you're infected by SARS-CoV-2. It could be one, two, three or more of the symptoms that health experts have pinpointed since the pandemic began, explains David Sullivan, M.D., an infectious disease specialist in the Department of Immunology and Molecular Microbiology at Johns Hopkins University.
Vaccinated individuals may experience any of the following symptoms during a breakthrough COVID-19 infection:
Fever and widespread chills across the body
Nasal congestion, runny nose and sore throat
Labored breathing, chest pain and respiratory congestion
Partial or full loss of taste and smell
Fatigue and joint pain
Diarrhea, nausea and vomiting
Vertigo and eye inflammation, although rarer among patients
Headaches, and what experts have coined as 'brain fog,' even into recovery periods
Difficulty multitasking or trouble focusing on a task at hand
You may experience a certain pairing of symptoms at the same time, or develop a certain side effect first before experiencing another — or, in asymptomatic cases, you may experience no symptoms at all. A breakthrough case is consistent with other outbreaks that have occurred in 2020 and beyond, and treatment remains largely the same as well, Dr. Sullivan adds.
Because vaccines have trained your body to mount a response to SARS-CoV-2, its response may cause you to experience symptoms later than usual. "A [vaccinated] person can still have a light infection typically with no symptoms, but a lower number of symptoms also," Dr. Sullivan explains. "We are still accumulating data on how often a vaccinated person can acquire the virus and pass it onto another person."
The Delta variant in particular has shown the capability of binding virus particles to what's known as the ACE2 receptor (a part of the cells located within your organs) much more efficiently than earlier versions of the virus. This is why breakthrough cases likely occur in the first place, Dr. Sullivan says, but adds that more research must be done to be sure.
Which breakthrough symptom is most concerning?
It can be difficult to distinguish some of the symptoms on this list — fever or coughing, headaches for example — as a sign of a SARS infection rather than, say, seasonal allergies. But there's one particular symptom that Dr. Sullivan has noticed consistently in his work with breakthrough illnesses: Loss of taste and smell.
The reason why partial or total loss of taste and smell is most concerning from a doctor's perspective is that it's more unique to COVID-19 cases than other illnesses. "The loss of taste or smell is extremely indicative of a SARS-CoV-2 infection," Dr. Montecalvo says. "Although there are many respiratory viruses, it's unusual for this particular symptom to happen — but it occurs commonly with this infection."
Losing your sense of smell or taste should prompt you to seek a COVID-19 test or to get help from your healthcare provider. "It's rare that tests return negative after the loss of taste or smell, as symptoms of a cold or flu with the sudden loss of taste and smell has a high probability of being COVID-19," Dr. Sullivan tells us. "But any onset of cold symptoms, or flu-like illness, should prompt you to seek a test."
It's not clear yet if losing your sense of taste or smell is common for breakthrough cases. Researchers have yet to present data suggesting Delta variant infections present any specific symptoms; and CDC officials are attempting to pinpoint patterns in current breakthrough illnesses, like a patient's sex, underlying conditions or which vaccine they received.
What to do if you believe you're experiencing a breakthrough COVID-19 infection:
It's best to seek out a local testing site near your home that can help you get tested, usually free of charge. You can access a full list of federally supported testing centers in your area using the U.S. Department of Health and Human Services' directory here.
According to CDC officials, you (or a caregiver) should only contact emergency services in the case that you have:
Difficulty breathing and unable to draw steady breath
Chronic pain or pressure in your chest or lungs
Confusion and inability to wake or stay awake
Skin discoloration in pale, gray, or blue hues, particularly on your lips or nail beds
Contacting your primary healthcare provider for help in arranging a test or to discuss your symptoms won't necessarily require you to seek out additional care. Dr. Montecalvo says that milder illness is likely for anyone who experiences a breakthrough COVID-19 infection, as vaccines are entirely effective at preventing death and stem severe cases from requiring hospitalization. You'll likely treat each symptom as they arise while resting at home, in addition to isolating yourself and remaining socially distant from family, friends, or roommates for a period of time to ensure the virus doesn't spread.
As more information about the coronavirus pandemic develops, some of the information in this story may have changed since it was last updated. For the most up-to-date information on COVID-19, please visit online resources provided by the CDC, WHO, and your local public health department.
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