Yes, you can get COVID again after having it, and it can happen sooner than most people expect. While your immune system does build protection after an infection, that protection isn’t absolute, and documented reinfections have occurred in as few as 17 days. The more practical answer is that reinfection within the first 90 days is uncommon but possible, and the risk climbs steadily after that window.
How Soon Reinfection Can Happen
The CDC notes that interpreting a new positive test within 90 days of a previous infection is difficult, partly because leftover viral material can trigger a positive result even when you’re no longer sick. But genuine reinfections within that window do happen. A study published in Emerging Infectious Diseases found that early reinfections with different variants occurred with a median gap of just 47 days, with the shortest confirmed case at only 17 days. One patient tested strongly positive with Omicron BA.1 just 39 days after a confirmed Delta infection.
These very early reinfections were most common in young, unvaccinated people and typically involved different variants. When a new variant is circulating that’s significantly different from the one you caught, the antibodies your body made the first time may not recognize it well enough to block infection entirely.
Why Your Immunity Fades
After a COVID infection, your body ramps up production of antibodies that target the virus’s spike protein. These antibodies peak roughly three to four weeks after symptoms start and hold relatively steady for about three months. After that, they begin to decline. By six months, only about 47% of people in one Canadian study still had detectable spike-targeting antibodies, and just 7% had strong neutralizing responses capable of blocking the virus effectively. Many people’s neutralizing antibodies disappeared entirely.
This doesn’t mean your immune system forgets COVID completely. Your body retains memory cells that can mount a faster response if they encounter the virus again. But that second response takes time to spin up, which means you can still get infected. You’re just less likely to get severely ill.
Reinfections Are Usually Milder
A large meta-analysis comparing reinfections to first-time infections found that reinfections were seven times more likely to be mild. The risk of severe illness dropped by 86% compared to a primary infection. Reinfection did not carry extra risk of hospitalization, ICU admission, or death. Among reinfected people in the pooled data, only about 0.6% developed severe illness, compared to roughly 5.5% during first infections.
When researchers looked specifically at reinfections occurring 90 or more days after the first infection, the hospitalization risk was even lower, about 67% reduced compared to primary infection. So the immune memory you build does meaningful work, even if it can’t prevent infection altogether.
Vaccination Adds a Layer of Protection
Having both a prior infection and vaccination (sometimes called hybrid immunity) provides stronger, longer-lasting protection than either one alone. But even hybrid immunity fades. After a primary vaccine series plus a prior infection, protection against reinfection drops to about 42% at 12 months. After a booster dose plus prior infection, it sits around 47% at six months. These numbers reflect protection against infection specifically. Protection against severe disease and hospitalization remains considerably higher and lasts longer.
Positive Test vs. New Infection
If you test positive shortly after recovering from COVID, it may not mean you’re infected again. PCR tests are extremely sensitive and can pick up fragments of viral RNA for weeks after you’ve stopped being contagious. These remnants aren’t live virus and can’t make you or anyone else sick, but they will trigger a positive PCR result.
Rapid antigen tests are more useful in this situation. They correlate better with the presence of actual infectious virus rather than leftover genetic material. If you’re past the acute phase of your illness, feeling better, and your rapid test turns positive again, that’s more suggestive of a genuine new infection than a lingering positive PCR would be.
Long COVID Risk With Repeat Infections
Each time you get COVID, there’s a chance of developing long-lasting symptoms. A retrospective study of healthcare workers found that the cumulative risk of long COVID among people who’d been infected was 17%. That risk increased with the number of infections. However, the picture is nuanced: reinfections were associated with 40% lower long COVID risk per episode compared to first infections, likely because reinfections tend to be milder. Omicron infections also carried 34% lower long COVID risk than earlier variants, and non-severe acute infections carried 72% lower risk than severe ones.
The takeaway is somewhat counterintuitive. Each individual reinfection is less likely to cause long COVID than your first infection was, but having more infections overall still increases your cumulative exposure to that risk. Reducing both the frequency and severity of infections appears to be the most effective way to lower long COVID burden over time.
Who Is Most Vulnerable to Reinfection
People whose immune systems don’t produce strong or lasting antibody responses face the highest reinfection risk. This includes people on immune-suppressing medications, those with conditions affecting B cells (the immune cells responsible for making antibodies), organ transplant recipients, and people undergoing cancer treatment. For these groups, the typical post-infection immunity window may be significantly shorter or weaker.
Unvaccinated individuals are also at higher risk. Without the additional immune training that vaccination provides, their antibody responses after natural infection tend to be narrower, targeting fewer features of the virus. That makes it easier for new variants to slip past their defenses. Young, unvaccinated people were overrepresented in the earliest documented cases of reinfection within 60 days.