Don’t shrug off that sneeze or scratch at the back of your throat. As
coronavirus
variants continue to evolve and become more difficult to detect, so do COVID symptoms, allowing more people to spread the virus without realizing it.
Signs of infection are increasingly hard to tell apart from symptoms of a common cold or flu, according to the latest update from the ongoing
Zoe Health Study, a joint project by
researchers
at Harvard, Stanford, and King’s College in London.
A mild runny nose, headache or sore throat could now precede a positive test result with one of the many offshoots of omicron.
Other indicators commonly reported during earlier phases of the pandemic, such as loss of taste and smell, have dropped down the list.
In addition to finding generally milder symptoms caused by omicron than earlier variants, the study showed that symptoms also varied by vaccination status.
For example, nasal congestion is the third-most-frequently-cited symptom in people who have completed their initial two-dose vaccination series, while those who have only received one jab reported sneezing, and for the unvaccinated, it’s fever.
“What changed is people’s overall immunity,” said Peter Chin-Hong, an infectious disease expert at UCSF who was not involved with the study. “On a continuous scale, as their bodies become more experienced with COVID, the symptoms are milder overall.”
In other words, the threat of the virus remains unchanged. But thanks to widespread immunity derived from the vaccines and prior infection, most people are now better equipped to fight off the most severe manifestations of the disease.
“Through painful steps — many deaths and millions of infections — as a population our immune system has become stronger and smarter,” said Jorge Salinas, an epidemiologist at Stanford, who was also not involved in the study. “Humans are not the same as in 2020. We now can recognize the virus and modulate the response to infection.”
Breaking down the data into three categories — fully vaccinated, partially vaccinated, and unvaccinated — the Zoe Health researchers found the four most commonly reported symptoms of COVID-19 among all the groups now are sore throat, runny nose, a persistent cough and headache.
“Generally, we saw similar symptoms of COVID-19 being reported overall in the app by people who had and hadn’t been vaccinated,” the researchers wrote. “However, fewer symptoms were reported over a shorter period of time by those who had already had a jab, suggesting that they were falling less seriously ill and getting better more quickly.”
So how did the lists differ? Here are the top symptoms by each group, based on daily data gathered by the U.K.-based Zoe app.
Fully vaccinated
1. Sore throat
2. Runny nose
3. Blocked nose
4. Persistent cough
5. Headache
One vaccine dose
1. Headache
2. Runny nose
3. Sore throat
4. Sneezing
5. Persistent cough
Unvaccinated
1. Headache
2. Sore throat
3. Runny nose
4. Fever
5. Persistent cough
Despite the evolving nature of the virus, the
Centers for Disease Control and Prevention website
still highlights loss of smell, shortness of breath and fever on its list of tell-tale signs of infection, even though they ranked at Nos. 6, 29, and 8, respectively, on the Zoe list for vaccinated individuals.
“A persistent cough now ranks at number 5 if you’ve had two vaccine doses, so is no longer the top indicator of having COVID,” the researchers said.
A
yearlong study
earlier this year of more than 60,000 people tested for the coronavirus in San Francisco found similar shifts in
COVID-19 symptoms
over time — including fewer reports of loss of smell, once considered a trademark of the illness.
More people reported symptoms of upper respiratory infection during the omicron surge than in earlier waves, according to the researchers at UCSF and the Chan Zuckerberg Biohub in coordination with
the San Francisco Latino Task Force. Patients also experienced fewer instances of systemic issues such as fever and body aches.
“Our report and others showed a transition happened with most common clinical symptoms with omicron to higher proportion of persons with congestion, more common to have sore throat, and less common to have loss of smell or taste compared to delta and prior variant,” said Dr. Diane Havlir, a UCSF infectious disease expert and senior author of the San Francisco study.
Salinas said these changes are to be expected: “It’s beginning to behave like other respiratory viruses.”
But as COVID-19 symptoms become milder and easier to ignore, the urgency to test becomes greater. Public health officials anticipate another swell in cases this winter with people spending more time indoors and traveling for the holidays.
Detecting positive cases early is vital to slowing the spread of the virus and preventing more immune-evasive strains of the virus from emerging.
There’s no guarantee that future variants will continue to cause milder disease, even among the vaccinated.
Chin-Hong said testing is also a good safeguard for high-risk individuals, especially if they run into potential delays in procuring treatments such as the in-demand antiviral medication Paxlovid.
“A lot of people are not getting diagnosed now because they don’t think it’s a big deal,” he said. “But getting a diagnosis will open the door to getting therapy.”
A previous version of this story misstated the most common symptoms for unvaccinated people and those with one dose.
Aidin Vaziri (he/him) is a San Francisco Chronicle staff writer. Email: avaziri@sfchronicle.com