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.

Several factors can influence reinfection, such as age, geographic location, and health equity.

Additionally, the World Health Organization (WHO) states that there may be an increased risk of reinfection from the Omicron variant in people who have previously developed COVID-19.

This article discusses current research regarding Omicron and other coronavirus variants, risk factors for reinfection, symptoms to watch for, and preventive measures people can take against reinfection.

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Omicron is a variant of SARS-CoV-2, the virus that causes COVID-19. The Network for Genomics Surveillance (NGS) in South Africa first reported it to the WHO on November 24, 2021. NGS first detected this variant in Botswana. Since then, it has become the predominant variant in circulation worldwide.

According to the Our World in Data COVID-19 database, the number of confirmed Omicron cases reported between December 2021 and March 2022 exceeded all previously reported cases.

One 2022 study states that the Omicron variant appears to cause less severe symptoms and have a shorter duration than previous variants. Additionally, people are less likely to experience long COVID from this variant.

Symptoms of COVID-19 due to the Omicron variant are so similar to those of other coronavirus variants that it makes the Omicron variant more difficult for healthcare professionals to detect through symptom-based testing or PCR testing alone.

Another difficulty in detecting this variant is the S gene, a predominant feature of the Omicron variant. In 2021, researchers noted that not all PCR tests could detect this gene.

The distinguishing marker of the Omicron variant is its spike protein, which contains 26 amino acid mutations. This contributes to its high transmissibility and vaccine resistance.

As scientists have only studied a dozen of the spike proteins present in the Omicron variant, it is still too early for them to gather information on other mutations and how these would affect the virus’s behavior. Research into the Omicron variant spike protein is ongoing.

A 2022 cohort study shows that although Omicron is a more transmissible variant, the number of deaths related to its infection rate and hospitalization figures are less than those of the original SARS-CoV-2 virus.

Like all virus variants, Omicron comprises several lineages and sub-lineages. A lineage is a group of closely related viruses with a common ancestor. In this case, it is SARS-CoV-2.

Omicron’s original lineage is B.1.1.529. However, there are other lineages and variants that are currently circulating. These include the BA.2, BA.4, and BA.5 variants.

There have been several variants of concern since the original outbreak of COVID-19. These include:

Beta variant (B.1.351)

The Beta variant first appeared in South Africa in May 2020 and spread to other countries. However, it did not become as common in the United States.

The Centers for Disease Control and Prevention (CDC) state that the Beta variant is about 50% more contagious than the original coronavirus strain.

Primary vaccinations were less effective against the Beta variant. However, while data on the effectiveness of booster vaccines that target the Beta protein spike is still limited, the Moderna booster vaccines appear to be more effective.

The Alpha variant (B.1.1.7)

The Alpha variant is 50% more transmissible than the original SARS-CoV-2 strain. The Alpha variant first appeared in Great Britain in September 2020.

Infections surged in December 2020, and Alpha soon spread around the world, becoming the dominant variant in the U.S. According to the CDC, the Alpha variant accounted for 66% of cases in mid-April 2021.

The Delta variant (B.1.617.2)

The Delta variant first appeared in India in October 2020. It soon spread throughout the world and became the predominant version of coronavirus until Omicron took its place in mid-December.

The Delta variant accounted for more than 99% of COVID-19 cases and led to an increase in hospitalizations. Unvaccinated people were at high risk of contracting the Delta variant.

Research states that vaccination is the best protection against the Delta variant.

The Gamma variant (B. or P.1)

The Gamma variant first appeared in Brazil in November 2020. Researchers estimated it to be 1.7 to 2.4 times more transmissible than other local strains.

However, it was less transmissible than the Alpha and Delta variants. Studies show that vaccinations are less effective against the Gamma variant than the Beta variant.

BA.4 and BA.5 sublineages

Scientists first detected these lineages in January and February 2022 in South Africa. Since then, experts have also detected these variants in other parts of the world, such as Austria, the U.K., the U.S., and Denmark.

These two lineages started the fifth wave of COVID in South Africa and accounted for 50% of cases.

The BA.4 and BA.5 lineages have an advanced growth rate due to the relative ineffectiveness of vaccinations. More research is necessary to see if these lineages will cause hospitalization.

Omicron sublineage BA.2

The Omicron sublineage BA.2 first appeared in March 2022. The WHO has classified this variant as a variant of concern due to its high transmission and reinfection rates.

This variant is currently the world’s most dominant variant and has a growth advantage over BA.1.

However, the BA.2 variant is less likely to reinfect those who have already contracted the BA.1 variant.

The following table summarises how effective the vaccines available in the U.S. are at preventing infection from certain SARS-CoV-2 strains, according to the CDC.

VaccineEffectiveness against infection
mRNA overall• 58% without prior infection
Pfizer-BioNTech• 67%, around 150 days after the second dose, pre-Delta
• 33%, around 150 days after the second dose, during Delta
Moderna• 75%, around 150 days after the second dose, pre-Delta
• 77%, around 150 days after the second dose, during Delta
Janssen• up to 17.8%, 2 weeks to 4 months after the last dose, during Omicron
• up to 29.2%, 2 weeks to 4 months after the last dose, during Omicron
Janssen/mRNA• up to 61.3%, 2 weeks to 1 month after the last dose, during Omicron

The CDC states that certain risk factors can make people susceptible to reinfection. These factors include:

  • Age: Older adults are more likely to get very sick from COVID-19.
  • Geographic factors: Some people are more at risk of contracting the virus because of where they live or work or because they cannot easily access healthcare.
  • Health equity: This includes discrimination and racism toward people from ethnic minority groups and education, income, and wealth disparity.
  • Previous infection of COVID-19: According to the WHO, evidence suggests that reinfection from the Omicron variant may be higher in people who have previously had COVID-19.

The CDC also states that several medical conditions lead to a higher risk of reinfection. These include:

The symptoms of Omicron are similar to those of previous variants. These include:

  • changes in the sense of taste and smell
  • cough
  • fever
  • shortness of breath
  • myalgia
  • fatigue and weakness
  • sore throat

Certain factors can affect the severity and duration of the Omicron variant, such as underlying health conditions, age, and history of prior infection.

People can help stop the spread of the Omicron variant — and protect themselves and others — by taking the following preventive actions:

  • getting vaccinated
  • improving ventilation
  • getting tested if symptoms are present
  • following government recommendations on how to manage personal exposure
  • avoiding contact with people who have a suspected variant
  • wearing a mask in public indoor spaces
  • socially distancing where possible

It is possible to contract Omicron twice. Many factors can influence reinfection risk, such as age, geographic location, and health equity.

Omicron is one of several variants of concern. Vaccination is more or less effective against different strains of COVID-19.

However, people should still receive their vaccinations and take further preventive actions such as wearing masks where possible and socially distancing. It is essential to follow all public health advice to reduce the risk of reinfection.