COVID-19 symptoms and the Delta variant
With the Delta variant now driving surges of COVID-19 cases worldwide, researchers are examining whether it's causing different symptoms from earlier variants and how it's experienced by vaccinated and unvaccinated people.
Severe breakthrough infections of COVID-19 remain uncommon, but a growing number of Americans are testing positive after being fully vaccinated, with some describing symptoms unlike those that marked earlier COVID waves.
"I started having flu-like symptoms Saturday night and went to the doctor this morning," Senator Lindsey Graham tweeted earlier this month, adding that he felt "like I have a sinus infection and suffered "mild symptoms." He thought that without the vaccine, "it would have been a lot worse."
Few described having COVID as similar to a "sinus infection" earlier in the pandemic. U.S. scientists have been examining whether fully vaccinated people experience different symptoms if they do come down with "breakthrough" infections caused by the variant, compared to earlier versions but have not yet issued any findings. The Delta variant is currently causing about 94% of the COVID cases in the U.S.
Do I have COVID-19, and are the symptoms changing?
One study suggests the symptoms may be evolving. The COVID Symptom Study, backed by the health science company ZOE in the U.S. and United Kingdom, has been collecting data on symptoms from millions of people and keeping a list of the most common symptoms reported by those who contracted COVID and were fully vaccinated, partially vaccinated or unvaccinated.
Nearly 74% of fully vaccinated contributors to the company's smartphone app reported having a runny nose when they had COVID, according to a video by one of the study's lead researchers posted in late July, as Delta variant cases were spiking in both countries. Headache, sneezing, sore throat, and loss of smell rounded out the rest of the top five symptoms for fully vaccinated people who contracted COVID.
Missing from that top-five list was coughing or shortness of breath, which were among the most frequently reported signs of COVID-19 early in the pandemic, before vaccines were available. A runny nose and sneezing were not commonly reported in initial cases.
However, not all recent studies of the Delta variant have turned up differences between cases in vaccinated and unvaccinated people.
The CDC's investigation of the outbreak in Massachusetts, which led to the discovery that fully vaccinated people with COVID had as much virus in their nose as the unvaccinated, documented "cough, headache, sore throat, myalgia, and fever" as the most common symptoms among 274 cases of fully vaccinated people who reported symptoms.
In the U.K., health authorities recently said the prevalence of "classic" symptoms — fever, cough, fatigue, and headache — among all cases of COVID-19 actually "appears to have increased in June and July 2021," when the Delta variant began to dominate most cases there.
"In terms of the symptoms that we see that are different between vaccinated versus unvaccinated individuals, the symptoms really remained the same," says Dr. Jack O'Horo, a critical care and infectious diseases specialist at the Mayo Clinic.
"We're still looking at initially cold-type symptoms like cough and fever. And people who have more severe infections, pneumonia-type infection symptoms," said O'Horo.
Could I have a severe breakthrough infection?
Probably not. Public health officials say breakthrough infections resulting in a hospitalization or death are still unlikely.
From January through June, the CDC estimated an average of 3.2% of hospitalized cases and deaths among adults overall involved fully vaccinated people, a finding similar to a recent Kaiser Family Foundation survey that found less than 3% of COVID-related deaths occurred among those who were fully vaccinated in many states.
But as cases spike among unvaccinated people, the number of severe breakthrough infections seems to be climbing, especially among those with serious underlying conditions. In June, the CDC found that 16% of hospitalized cases and 22% of deaths in June occurred in fully vaccinated people, in a preliminary analysis of data sampled from its COVID-NET surveillance system.
Louisiana entrepreneur Angelle Mosley, who died at 33 in late July, was among the 0.0009% of vaccinated Americans whose breakthrough COVID cases prove fatal. Her mother told CBS News that her weight was a factor in her death.
"It's very important for every single person who's been vaccinated to know, if you have other medical conditions, the vaccine doesn't protect from those becoming an issue or causing a problem," said CBS News medical contributor Dr. David Agus. "While the vaccines may give you some protection, it's not enough to overcome the medical issues or the lack of a very strong immune system, unfortunately."
For many, advanced age also plays a role. "These hospitalized cases include many adults age 65 years and older; given the high vaccination coverage in this age group (>75%), these numbers still indicate vaccines are very effective," Jade Fulce, a spokesperson for the CDC, said in an email.
Is my vaccination still keeping me from getting severe COVID?
Almost certainly, although preliminary findings from the U.K. and Utah, as well as a multistate network of hospitals, that must still be peer reviewed, do suggest that vaccine effectiveness against severe disease may decline by a few percentage points over time and in the face of the variant.
But that shouldn't stop people from getting their vaccine shots, doctors say.
"Right now, the majority of cases where we are seeing positive with COVID-19 are the unvaccinated. Period," said Agus.
Around a third of the COVID-related hospitalizations among vaccinated adults were in immunocompromised patients, the CDC also recently said. The FDA last week authorized an additional dose for these Americans in hopes of boosting their protection.
If I've been vaccinated and I contract COVID, what are the chances I'll have symptoms?
It could be at least 1 in 5,000.
Last month the CDC estimated that 35,000 symptomatic breakthrough infections were occurring every week in the U.S. among 162 million fully vaccinated Americans, according to leaked slides first reported by The Washington Post.
Months of research and real-world evidence previously suggested most fully vaccinated people would face similar but milder versions of the same disease sickening unvaccinated people.
One recent study led by the CDC's Mark Thompson, closely following essential and frontline workers through April, found the risk of symptoms and duration of illness was much lower among most vaccinated participants with breakthrough cases.
Thompson said in an email that the CDC is still studying breakthrough COVID symptoms among Delta variant cases will report on them "as soon as we can."