Study Shows Omicron Is Most Infectious 3-6 Days After Onset of Symptoms

Since its detection, the COVID-19 variant Omicron quickly caused surges in cases worldwide. In the Philippines, officials believe that Omicron is now the dominant variant, replacing the feared Delta. And while there are speculations that it’s less severe than its predecessors, there’s no doubt that Omicron is highly transmissible. Recently, a small study in Japan noted that the peak infectiousness of Omicron is at 3 to 6 days from the onset of symptoms. What does this mean for us? Find out here. 

New Study Identifies the Peak Infectiousness of Omicron¹

A Japanese study looked into the viral load of 21 patients infected with the Omicron variant. 

They observed that the patients had the highest viral load 3 to 6 days after the onset of symptoms. Likewise, they noted that the load was consistently high after 7 to 9 days. 

However, the researchers were not able to culture live viruses from the samples on the 10th day despite still detecting the viral genetic material. This suggested that none of the patients were infectious at that stage. 

Note that of the 21 participants, 19 were fully vaccinated. Four patients didn’t develop symptoms while the rest had mild symptoms. 

The Problem With the Peak Infectiousness of Omicron

If the peak infectiousness of Omicron is at 3 to 6 days after the onset of symptoms, with high viral levels by days 7 to 9, then we might not be reducing the spread of Omicron by shortening the isolation for those who already completed 2 doses of their COVID-19 vaccine. 

Per the updated protocol³, asymptomatic general public and healthcare workers need to go into isolation for 7 days after the onset of their symptoms if they are fully vaccinated. Asymptomatic close contacts with full vaccination only need to isolate themselves for 5 days. 

Remember that the majority of the participants in the Japanese study were also already fully vaccinated. 

The Good Points: Omicron Might Be More Transmissible, But Less Lethal

Since the Japanese study is fairly small, with only 21 participants, the government may not revise the new isolation protocol anytime soon. After all, even the newest recommendations from the Centers for Disease Control (CDC) suggest a shorter isolation duration. Asymptomatic patients – regardless of vaccination status — only need to isolate for 5 days. 

At this point, shorter quarantine guidelines should not cause panic, especially since studies show that Omicron appears to be less lethal than Delta. 

In one research involving 97 confirmed and suspected Omicron cases and 107 Delta infections, the researchers concluded that⁴:

• The mean duration for Omicron was 9.87 days and 10.9 days for Delta. 
• Omicron’s peak viral load is lower than Delta’s peak viral load.
• The clearance phase is shorter for Omicron than Delta. 

Reports also say that the Omicron is more likely to infect the throat than the lungs, and this might make the variant less lethal. This could explain why it’s so transmissible and why a South African study noted that saliva PCR tests are better in detecting the Omicron than swabs⁵. 

But this should not make the public complacent. Omicron is still fairly new, so studies are ongoing. Experts also emphasize that Omicron can still lead to hospitalization.

What To Do for Now

We might need more studies to confirm the peak infectiousness of Omicron. For now, it’s best to follow the guidelines set by experts and officials. If you receive exposure to someone with COVID-19, isolate immediately and have yourself tested when possible. If you develop symptoms, isolate for at least 10 days. 

Of course, get your primary COVID-19 shots and the booster dose. Vaccination is still the best way to prevent severe infection, hospitalization, and death. 

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