By Professor Leo Yee Sin, Executive Director, National Centre for Infectious Diseases (NCID); Adjunct Associate Professor Matthias Toh, Director, National Public Health and Epidemiology Unit (NPHEU), NCID; & Associate Professor Raymond Lin, Director, National Public Health Laboratory (NPHL), NCID

Just as the number of new community cases in Singapore are on its way down, the whole world is once again jolted by the announcement of a new variant of concern named Omicron by the World Health Organization (WHO), after the letters of the Greek alphabet.

Applying the lessons from Delta

The Delta variant has taught the world many precious lessons. These include the importance of a strong surveillance system with ability to sequence genomes, transparent and rapid sharing of information to out-pace the speed of the virus spreading within and outside of respective geographical regions, maintaining a healthy collaborative network, and preparedness to mount an effective response rapidly. Last but not least, is to do all we can to achieve the highest vaccine coverage in addition to the many non-pharmaceutical interventions familiar to many of us today. Speed is of the essence when dealing with SARS-CoV-2.

The WHO was informed expediently after the discovery of an unusual genome sequence from a rapidly expanding cluster in South Africa. Learning from the experience of dealing with the Delta variant, an urgent meeting was convened by the WHO within two days on 26 November. The initial genomic and epidemiological findings were scrutinised and found to be astonishing, to the extent that it prompted the international expert body to classify the new discovery as a variant of concern even though its full characteristics were still largely unclear. Within hours, the WHO released its official statement announcing the arrival of Omicron variant.

Barely one week later, many countries including Singapore reported the detection of Omicron. This new variant has over 30 mutations in its spike proteins. Spike or S protein is the outer part of the virus which attaches to human cells that express certain receptors such as the ACE-2 receptor. On the other hand, S protein is the key target which blocks viral invasion on to human cells. S-protein can be achieved through vaccination to elicit antibodies or infusion of monoclonal antibodies. Some of the S gene mutations are located close to the target region. This raises an urgent need to study whether Omicron will alter the effectiveness of the current COVID-19 vaccines. Nonetheless, with current knowledge, we know that a higher antibody level provides better protection against SARS-CoV-2 infection including against different variants. The early reports also suggested that majority of the severe cases related to Omicron were not vaccinated.  We need to urgently vaccinate and boost the individual and community immunity levels through vaccination, with the hope of reducing infection and disease severity.

Solving the mystery of Omicron

It is timely that international networks join hands to crack the mystery of this new variant. First, we need to learn of its origin to understand how this virus silently morphed into an extremely fit pathogen with increased transmissibility. This could be fuelled partially by its ability to evade full protection from pre-existing immunity and explain the higher ratio of re-infected cases as reported in South Africa.

Next and more importantly, we need to monitor the impact of disease severity caused by Omicron. Thus far, many anecdotal reports suggest a milder disease. However, we still do not have sufficient clarity whether Omicron causes age-differentiated disease severity like the other variants of concern and we lack the full picture on re-infection or post-vaccination infection. It is also crucial to learn how Omicron will respond to current therapeutic interventions, including the use of existing medication such as remdesivir, and the newer drugs that are fresh from the oven such as MSD's molnupiravir and Pfizer's paxlovid. Perhaps there is some comfort in knowing that these drugs are not targeting the S gene and are likely to retain its effectiveness. Immune modulators and anti-coagulants currently being used will continue as per its current indications. But studies are required to address whether Omicron may alter host immune response. At present, we do not anticipate a major change in clinical management.

We have learnt that SARS-CoV-2 is extremely unpredictable and full of surprises. It behaves very differently from influenza and is not to be underestimated. This understandably makes long term planning a huge challenge. Hence, it is important for all of us to stay alert, nimble and flexible to changes even though these have caused some degree of inconvenience. As of now, while we may be alarmed by Omicron, we should not panic. We have accumulated past experiences in dealing with SARS-CoV-2, and have established counter-measures including safe management measures and technologies to update vaccine in our tug-of-war with the virus. It is also timely to remind the community to go for influenza vaccination so as to use the available means to keep us safe from respiratory illnesses.

The article was also published in Lianhe Zaobao on 4 December 2021.