On 25 November, the African Union and Africa Centers for Disease Control and Prevention released a statement that identified the Omicron variant as the newest variant of concern (VOC). It is also known as the B.1.1.529 variant1. On the next day, the World Health Organization (WHO) issued its own statement, labeling it a VOC2. Since then, it has become the predominant variant or strain, causing as much as 98% of all new Covid-19 cases in the USA3. It is much more infective than the previously predominant Delta variant, but usually causes much milder symptoms of Covid-19. The Omicron spike protein has a more compact structure than the previously dominant Delta strain4. This improves the stability of the Omicron variant and enhances its attachment to human cells, but reduces fusion with them. These differences probably cause the 50–90% reduction in risk of hospitalization and mortality of Omicron relative to Delta4. Omicron patients are significantly younger, had significantly increased vaccine breakthrough rates, and were significantly less likely to be hospitalized3. Then, a new Omicron sublineage was detected in South Africa on 7 December4. It was originally called 21 L, Omicron (21 L, BA.2), but BA.2 is more commonly used in more recent reports5-8. Its spike protein contains 29 amino acid substitutions and one insertion4. Compared to the Omicron (21K, BA.1), the Omicron (21 L, BA.2) spike protein has amino acids 69–70, which are deleted in the BA.1 lineage. So, it is not detected by the S Gene Target Failure (SGTF) assay and is called the stealth variant4,10. So, the B.1.1.529 lineage has been subdivided into BA.1 and BA.25. People who have been previously infected by a different strain (such as Delta) or have been vaccinated are not as well protected against infection by the Omicron variants11. The BA.2 variant is resistant to 17 of 19 neutralizing monoclonal antibodies that were tested, including S309, also known as sotrovimab, which is still active against the BA.1 variant12.
The BA.2 lineage has begun to spread in the USA, Hong Kong and other places in the world. It accounted for about 12 % of newly diagnosed cases of Covid-19 in the USA from 8–15 March. The increase has been limited by the fact that about 45% of people in the USA have already been infected by the Omicron BA.1 variant and have developed immunity that is also effective against the BA.2 variant. Still, vaccination almost always keeps the infection by the SARS-CoV-2 virus from causing a severe case of Covid-19. This is especially true for people who have received not only the two recommended doses of a vaccine, but also a booster shot4,13. So, the emergence of BA.2 is another reason for the unvaccinated and unboosted to get a shot. Still, in the land of the free and the home of the brave, people are free to reject this advice, spread lies that influence their friends and risk suffering a miserable death caused by Covid-1914.
The highly contagious BA.2 variant has caused a huge increase in the number of infections, especially in Hong Kong, where the Covid-19 pandemic had been relatively mild. Now, it’s the world’s hot spot with a death rate exceeding 25 per 100,000 people from 8–15 March. The high rates of infections and deaths are due to vaccine skepticism. Only about 40 % of Hong Kong’s population is not vaccinated and more than 50% of people over 70 are unvaccinated. Most of the people who are vaccinated received the Chinese Sinovac vaccine. It protects against severe illness, but not as well as many Western vaccines, such as Pfizer/BioNTech’s and Moderna’s mRNA vaccines6. Covid-19 is also spreading in New Zealand, Singapore, South Korea and other Asian and Pacific countries that had previously kept infections and deaths very low. The death rates in those countries are lower than that of Hong Kong because of higher rates of vaccination. At the same time, the number of cases is rising in England, Germany, Italy and some other European countries, while it has fallen in the USA. Still, many unvaccinated people continue to die.
As a final note, I would like to express my sympathy for the people of Ukraine who are suffering from the violent aggression perpetrated by the Russian army under the command of Vladimir Putin. It is remarkable how he has done what no politician in the USA has been able to do. He has brought together Republicans and Democrats as well as the European Union, Japan and even Switzerland in their sanctions and strong condemnation. He has also made Donald Trump yesterday’s news.
1 African Union, Africa Centres for Disease Control and Prevention’s statement regarding the new SARS-COV-2 virus variant B.1.1.529, 25 Nov., 2021.
2 World Health Organization. Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern. 26 November 2021.
3 Christensen PA et al. Signals of significantly increased vaccine breakthrough, decreased hospitalization rates, and less severe disease in patients with Coronavirus Disease 2019 caused by the Omicron variant of severe acute respiratory syndrome Coronavirus 2 in Houston, Texas. American Journal of Pathology, 10 Feb., 2022.
4 Simon-Loriere E & Schwartz O. Towards SARS-CoV-2 serotypes? Nature Reviews Microbiology, 2022.
5 Tian D et al. The emergence and epidemic characteristics of the highly mutated SARS‐CoV‐2 Omicron variant. Medical Virology, 2022.
6 Lu L et al. Neutralization of SARS-CoV-2 Omicron variant by sera from BNT162b2 or Coronavac vaccine recipients.
7 Yamasoba D et al. Virological characteristics of SARS-CoV-2 BA.2 variant. bioRxiv preprint, 15 Feb,, 2022.
8 Zhou H et al. Neutralization of SARS-CoV-2 Omicron BA.2 by therapeutic monoclonal antibodies. bioRxiv preprint, 24 Feb., 2022.
9 Lyngse FP et al. Transmission of SARS-CoV-2 Omicron VOC subvariants BA.1 and BA.2: Evidence from Danish Households. medRxiv preprint, 2022.
10 Vidya NM et al. S Gene Target Failure (SGTF) in Commercial Multiplex RT-PCR assay as indicator to detect SARS-CoV-2 VOC B.1.1.7 lineage in Tamil Nadu, India. medRxiv preprint, 16 Dec., 2021.
11 Cele S et al. SARS-CoV-2 Omicron has extensive but incomplete escape of Pfizer BNT162b2 elicited neutralization and requires ACE2 for infection. medRxiv preprint, 17 Dec., 2021.
12 Iketani S et al. Antibody evasion properties of SARS-CoV-2 Omicron sublineage. Nature, 28 Feb., 2022.
13 Singanallur NP et al. At least three doses of leading vaccines essential for neutralisation of SARS-CoV-2 Omicron variant. medRxiv preprint, 25 Feb., 2022.
14 Smith, R.E. Freedom during the Covid-19 pandemic. Humans debate, while viruses mutate freely. Wall Street International, 24 Dec., 2021.