My family got Covid. So why did we test negative?

Why do some people come down with Covid-19 symptoms but never test positive? Photo / Bevan Conley

As a science journalist, I've read dozens of research papers about Covid-19, and I've interviewed so many virologists, infectious disease physicians and immunologists over the past two years that I've lost count. But nothing prepared me for what happened after my 7-year-old daughter tested positive for Covid-19 nearly two weeks ago.

It started the way you might expect: On a Sunday evening, my daughter spiked a fever. The next morning, we got an email informing us that she'd been exposed to the coronavirus on Friday at school. I gave her a rapid antigen test, which quickly lit up positive. I resigned myself to the possibility that the whole family was, finally, going to get Covid-19.

But we didn't — not exactly. I, for one, never developed symptoms or tested positive. On the day my daughter first tested positive, my 11-year-old son announced that he wasn't feeling well and began developing classic coronavirus symptoms: headache, fatigue, sore throat, runny nose. My husband followed two days later with a sore throat and stuffy nose. Yet despite testing daily for seven days straight, my husband and son never tested positive for Covid-19 — including on PCR tests administered on my son's fifth day of symptoms, and my husband's third. (And yes, we did some throat swabs, too.)

We racked our brains as to what might have happened: Did my husband and son get Covid, even though they never tested positive? Or did they have another virus that caused identical symptoms and happened to infect them right after they were exposed to Covid-19? (Our paediatrician said that was unlikely.) Why hadn't I gotten sick at all? I called experts in immunology, microbiology and virology to get their take.

Vaccination changes how your body reacts to the virus

One of the first questions experts asked me was whether my family was vaccinated. Yes, I said: My husband and I are vaccinated and boosted, and our kids are vaccinated but not yet boosted. This is a relevant question because, if you're exposed to the virus that causes Covid-19, "your immune system kicks into action a lot faster if you're vaccinated versus not vaccinated," said Gigi Gronvall, an immunologist at the Johns Hopkins Center for Health Security in Baltimore. And this rapid response changes everything about what happens next.

First, the swift immune reaction slows the rate of viral reproduction and spread. "This is what the vaccines are there for — to educate your immune system so that it gets a jump on the invaders before they are able to replicate out of control," Gronvall said. Because the virus doesn't replicate as quickly in vaccinated people, they may be less likely to test positive for Covid-19 after coronavirus exposure, because their immune system "keeps the viral load below the level of detection," said Juliet Morrison, a microbiologist at the University of California, Riverside.

It's possible, then, that my husband and son did catch Covid-19, but their vaccinated immune systems fended off the infection so well that they never had enough viral proteins in their nose or throat to test positive. And their negative tests probably meant that they were never that contagious, Morrison said.

Still, my husband and son followed the guidelines from the Centers for Disease Control and Prevention, which say that if you're vaccinated, have been exposed to Covid-19 and develop symptoms but test negative, you should continue to wear a mask around others for 10 days. In fact, everyone in the house who was symptomatic stayed out of public for seven days. I ran a few errands but wore an N95 or KF94 mask when I did, in case I was incubating an infection.

To reduce spread between family members, we opened the windows, ate outdoors and wore masks around each other when we remembered — but I'll be honest and admit that our precautions relaxed after several days, especially once my husband and son developed symptoms, too.

You can feel sick even if the virus is under control

If my husband and son never tested positive, why did they feel sick? Even if a vaccinated person doesn't have much virus in their body, they can still have powerful Covid symptoms, the experts told me. That's because many illness symptoms — fever, malaise, runny nose, fatigue — are actually caused by the immune system's response to the virus, rather than the virus itself, Gronvall said.

And as for why I felt fine, Morrison said that perhaps my immune system fought off the incoming virus so quickly that I didn't even have a chance to feel sick.

"It sounds to me like you were definitely exposed," Morrison told me. But, she explained, maybe I had high levels of vaccine antibodies or immune cells called T cells that were able to kill the invading virus before it had a chance to alert the parts of my immune system that would incite symptoms.

All this said, nobody really knows what happened to me, my son or my husband.

When it comes to understanding how Covid-19 affects the body, "there are so many open questions," said Raul Andino, a virologist at the University of California, San Francisco, and people can have different experiences for many different reasons. For instance, Andino said, it's possible that the virus was replicating in parts of my husband's or my son's body that the tests didn't reach. Research suggests that the coronavirus can replicate in the pancreas, heart, brain, kidneys and other organs, although vaccination may reduce the chance that the virus spreads outside the respiratory system.

My family is not the only one that has had the bizarre experience of developing coronavirus symptoms but repeatedly testing negative. Andino said that he and his colleagues have been conducting studies in which they follow and repeatedly test entire households after one person in the home tests positive for Covid-19.

"What we see is exactly what you described — that some people in the household don't test positive," even though they have symptoms, he said. When I asked my Instagram followers if they'd had an experience like my family's, I got dozens of "yes" replies and stories that sounded a lot like ours.

Most people with Covid-19 exposure and symptoms will test positive, eventually

The experts I talked to also made a really important point: There's a difference between never testing positive and not yet testing positive. My husband and son continued to test themselves for a week after developing symptoms, so my sources said it was unlikely they were ever going to test positive. But many people only test for a couple of days and, frustratingly, you can't make clear conclusions from just a couple of negative tests.

As I said earlier, when people are vaccinated against Covid-19, their immune systems are primed to fight it quickly, and they often develop symptoms earlier than unvaccinated people do — a few days before they can test positive. So when people only test a few days after developing symptoms, their negative results don't necessarily mean they don't have Covid-19. Yet some people assume at that point that they don't have the coronavirus and stop taking precautions.

"They may relax mitigation measures when they are still shedding quite a bit of virus," Gronvall said.

Given these findings, Gronvall said that, ideally, people who have had two or three vaccine doses should test once they start developing symptoms but continue to test on day four or five of symptoms, as tests that come back negative before then may be falsely reassuring. To do this, however, you need to have access to lots of tests.

As for our family, everyone has now fully recovered. The mystery of what transpired in our home continues to eat at me, but it's far outweighed by my relief that we had such a mild experience — and for this, we have our Covid-19 vaccines to thank.

This article originally appeared in The New York Times.

Written by: Melinda Wenner Moyer
© 2022 THE NEW YORK TIMES