The answer boils down to one key factor: Their mutations allow them to re-infect people who have already had an omicron infection. This reinfection risk may be higher for people who are not vaccinated.
Protection highest after booster
Pooled VE against Omicron infection in children was 46.3%, with a VE of 18% after the first dose and 50.7% after the second. Among adolescents, VE against infection was 54.4%, with 39.1% VE after the first dose, 60.6% after the second, and 63.4% after a booster.
There is waning immunity
“As we went from the Alpha to Delta to Omicron, we have reduced our ability to prevent reinfection and so we can get infected again.”
Unfortunately, the higher contagiousness of the Omicron variants upended that protection. “The risk of reinfection starts quite reasonable, like 76% at the first month, but up to 10 months it drops to 36%” following an Omicron infection, said co-author Dr.
Is it possible to get Omicron twice? The Omicron variant spreads easier than other variants of coronavirus, and people can get it twice. Reinfection is possible even if a person has already had this virus or is fully vaccinated.
A few recent studies have shown it's possible to get reinfected with another variant (or even another omicron subvariant) in as little as 20 days; back in January, Slate ran an account of a woman who was likely infected with delta one month and omicron the next.
The same disease that took time - at least 6 to 9 months - to reoccur, is now capable of reinfecting a person much sooner. While earlier, we could be worry-free and relieved once we recovered from COVID-19, it is not the same now, given that people are getting infected time and again.
The effectiveness of previous pre-omicron infection, followed by BA. 1 or BA. 2 infection, against BA. 2.75 reinfection was 56.4% (95% CI, 50.5 to 61.6).
You can also spread COVID-19 in the 48 hours before your symptoms start. If you never have symptoms, consider yourself most infectious in the 5 days after you test positive.
Since it's been estimated that over 80% of Americans have been infected with COVID-19 at least once, concern about reinfection is valid. Indeed, a person can get COVID-19 once, twice, three times or more. Does looking at the impact of reinfection matter, especially if you've been vaccinated? Absolutely.
If you experience rebound symptoms, you are likely contagious again. You should isolate yourself to prevent passing the disease to others. For more information, consult your doctor or the CDC guidelines.
After your body's disease defense system (the immune system) fights off a virus, it keeps a memory of it. A study suggests that people's immune systems remember COVID-19 for months after recovery.
The original Omicron strain (BA. 1) was first identified in Botswana and South Africa in late November 2021, and cases quickly began to surface and multiply in other countries.
People with moderate or severe COVID-19 should isolate through at least day 10. Those with severe COVID-19 may remain infectious beyond 10 days and may need to extend isolation for up to 20 days.
You are contagious for the entire period of time symptoms are present, all the way until they disappear.
Sometimes, people can get a positive COVID-19 test result even though they no longer have COVID-19. This is because people with COVID-19 have infected cells in their body that release the virus into the environment through breathing, sneezing or coughing, or through their faeces and urine.
We identified 188 (0.7%) cases of reinfection out of 27,972 patient samples that tested positive for the SARS-CoV-2 Omicron variant during November 28, 2021–July 22, 2022.
There have been some cases of second infections reported. Even if you have had mpox in the past, you should be doing everything you can to avoid getting re-infected.
Data from long-term studies showed that protection against reinfection for pre-omicron variants dropped to 78.6% over 40 weeks, whereas for omicron BA. 1 it dropped more rapidly to 36.1%. When assessing severe disease, however, all variants showed sustained protection above 88% for 40 weeks.
Some people can test positive for COVID-19 for weeks or even months on PCR tests, but there is good news: people are not likely to be contagious for that long from a single infection, even if they test positive, and therefore are unlikely to transmit the virus to others.
Memory immune responses
After the first encounter with a pathogen, our immune systems generate a small number of cells that remain for a long time, are specific for that pathogen, and circulate in the blood, spleen and lymph nodes to keep watch for another encounter.
An antibody is a protein component of the immune system that circulates in the blood, recognizes foreign substances like bacteria and viruses, and neutralizes them.
To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies. Not mRNA vaccines. Instead, mRNA vaccines use mRNA created in a laboratory to teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies.
People with Long COVID can have a wide range of symptoms that can last weeks, months, or even years after infection. Sometimes the symptoms can even go away and come back again.