Delta vs. Omicron: How Do These COVID-19 Variants Differ?

⮂ Share

Since the start of the COVID-19 pandemic, the SARS-CoV-2 coronavirus that causes the disease has mutated several times, resulting in different virus variants. Two of these variants that have been making the headlines worldwide are Delta and Omicron.

The Delta variant was first identified in India in late 2020, and it spread rapidly through that country and Great Britain before reaching Asia, where it caused a rapid rise in COVID-19 cases. It also led to a severe strain on health infrastructure in some countries. The Delta variant has already been identified in at least 132 countries around the world.

Like Delta, Omicron swept rapidly through many countries, and in just a matter of weeks, it has already surged around the world. The Omicron variant was first reported in Botswana and South Africa in November 2021.

Omicron is said to spread faster than any previously known mutation of the coronavirus. Today, it is already causing an unprecedented rise in new cases that may push some healthcare systems to the breaking point.

What exactly is the difference between the Delta and Omicron variants? Is one strain more dangerous than the other? Read on to learn more about these different forms of the coronavirus and how you can protect yourself from them.

Delta’s transmission rate

To determine the transmissibility of an infectious virus, you need to look at its R0 or Basic Reproduction Number. Pronounced as “R naught,” this mathematical term indicates how contagious a virus is. It also tells how many other people a single infected person will pass the virus on to.

For delta, the R0 has been identified as at 5-8. This means that, on average, one infected person can pass the virus on to 5 or 8 others. This is comparable to the R0 of the original coronavirus strain, which has been determined to be at 1.5-3. In other words, Delta is twice to five times more contagious than the original virus that spread in 2020. 

Symptoms and severity of Delta

When talking about symptoms, it is essential to remember that Delta and Omicron are still the same SARS-CoV-2 virus. While specific symptoms may appear more noticeable or prominent in one strain than the other, the symptoms of all COVID-19 variants will be mostly similar.

According to the Centers for Disease Control and Prevention (CDC), people infected with the coronavirus can manifest various symptoms, spanning from mild to severe illness. In general, here are the most common symptoms of COVID-19:

  • Fever and chills
  • Dry cough
  • Fatigue
  • Headache
  • Aching of muscles or body
  • Sore throat
  • Loss of taste or smell
  • Shortness of breath
  • Blocked or runny nose
  • Nausea or vomiting
  • Diarrhoea

Loss of taste or smell is an additional symptom that CDC included only in April 2020. It can be seen in a significant number of Delta patients. Aside from this, the signs of the Delta strain are often just the same as those of a common cold, such as fever, cough, and headache. These symptoms usually appear among the unvaccinated, as vaccinated people typically have very mild symptoms or are asymptomatic.

In terms of severity, some studies have shown that infections during the predominance of the Delta variant were significantly more severe than those during the Omicron variant. The risks for hospitalisation, ICU admission, and death were also found to be greater among patients with the Delta variant. In other words, many experts suggest that the Delta strain brings more severe symptoms compared to the incomer Omicron.

Omicron’s transmission rate

Since Omicron is a relatively new mutation of the coronavirus, there is still no specific R0 for this variant. However, one thing that experts are now sure of is that this form of coronavirus is much more contagious compared to the other previously known strains. This is partly because Omicron is far better at evading the current vaccines than the different variants.

Notably, according to a recent study done by the researchers at the University of Copenhagen, Statens Serum Institut (SSI), and Statistics Denmark, Omicron is 2.7 to 3.7 times as contagious as the delta variant among vaccinated individuals. For the experts at the London School of Hygiene and Tropical Medicine, the R0 of Omicron can be as high as 10.

Symptoms and severity of Omicron

There is still no conclusive data on the common symptoms of Omicron, but one thing that many experts are already almost sure about is that this new COVID-19 strain is less severe than the previous variants.

According to data from the United Kingdom, fever and cough are less prevalent in omicron cases, while fatigue, headaches, runny nose, sneezing, and sore throat are more common.

Moreover, unlike patients with Delta and other previous COVID-19 strains, those with Omicron are less likely to experience loss of taste or smell.

However, while most COVID-19 symptoms are less prominent and severe in Omicron cases, observations by some medical professionals suggest that a new sign is emerging among a significant number of omicron patients: night sweats or repeated episodes of extreme perspiration.

For several experts, the decreased severity of Omicron can be attributed to the assumption that this new variant is less likely to invade a person’s lung tissue. There is evidence that Omicron leads to minor pneumonia and less severe disease.

Hence, compared to delta cases, omicron cases were reported to have fewer risks of hospitalisation, ICU admission, and death. A study funded by CDC using data from the Kaiser Permanente Southern California health care system mainly found that none of the more than 50,000 omicron patients it observed required mechanical ventilation.

Nonetheless, many experts still cautioned that while Omicron appears to be less severe than Delta, especially among those vaccinated, it does not mean that it should be classified as “mild.”

Like Delta and the other previous COVID-19 variants, Omicron still hospitalises and kills people.

How effective vaccines are against these variants

The data shows that vaccine effectiveness decreases with both the Delta and Omicron variants. When Delta became predominant in the early months of 2021, the efficacy of many vaccines fell to an estimated 66%.

However, several researchers believe that this may signify that the protection wanes over time. Hence, full doses and booster shots are highly encouraged to avoid severe Delta and Omicron cases.

So far, the data provides that a complete course of the AstraZeneca, Moderna, or Pfizer vaccines can lower a person’s chance of severe COVID-19 disease, which requires hospitalisation, by more than 85%. Although the protection is lower for Delta than the original strain, studies show favourable coverage for all vaccines after at least two doses.

On the other hand, when it comes to Omicron, two doses of vaccines like Moderna and Pfizer are found to provide much less protection. A booster shot after full vaccination is needed to ensure stronger protection against severe omicron infection.

Recent data has already confirmed that a booster shot increases the production of antibody and enhances the effectiveness of vaccines against infection to about 75% and 88% for severe disease.


While the strains of COVID-19 can differ in transmission, symptoms, and severity, people need to remember that they are all still the same SARS-CoV-2 virus that has caused significant damage to the global population for more than two years now.

Despite the differences in variants, the main preventive measures remain the same: receiving vaccines, wearing face masks, and social distancing.

If you are experiencing any of the symptoms of COVID-19, it is best to isolate yourself right away and take a virtual ART test in Singapore. Immediate self-isolation, medical consultation, and testing are the keys to preventing the further spread of the virus. Fortunately, you can now quickly consult an online doctor with the help of the MyCLNQ app.

Considered the leading one-stop telemedicine provider in Singapore, MyCLNQ provides a wide range of healthcare services that you can access anytime, even while staying in your home’s comforts.

Whether you need to buy medicines online, hire a private ambulance service in Singapore, or schedule an online medical consultation, you can use the MyCLNQ app for your convenience and safety.

⮂ Share