By Emeritus Professor Lam Sai Kit

 
KUALA LUMPUR, Malaysia: The doubling of Covid-19 cases in both Malaysia and neighboring Singapore in recent weeks has sparked fear of a renewed surge in both countries, recalling days of the early pandemic. Other countries in the WHO Western Pacific Region which reported increase are Australia, New Zealand and Brunei. However, based on the WHO Covid-19 Epidemiological Update of 24 November, the number of reported cases and deaths globally during the 28-day period from 23 October to 19 November 2023 compared to the previous 28 days have decreased by 13 percent and 72 percent respectively.
 
“As a matter of fact, only the WHO Western Pacific Region showed an increase of 14 percent (130,000 new cases) during the latest 28-day period while the number of cases decreased across the other five WHO Regions. “The situation may change with the increase in year-end holiday travels, especially those traveling to countries experiencing winter conditions.”
 
According to the Ministry of Health Malaysia, the number of Covid cases was reported to have increased from 6,796 cases to 12,757 cases between December 3 to 9. In Singapore, the estimated number of Covid infections doubled to 22,094 from 10,726 in the week between November 19 to 25.
 
Besides asking the Malaysian public to mask up in crowded indoor areas and to practice good hand hygiene, the MoH is also asking the public to ensure they are adequately vaccinated against Covid, including getting a second booster dose for those who have yet to receive it. This is especially important for the elderly, those with pre-existing health conditions, those immune-compromised and those with comorbidities such as diabetes and heart diseases.  
 
MoH Malaysia still has ample stock of the original Covid vaccines and would like to offer this as booster shots. Any new order for Covid 19 vaccines should take heed of the WHO statement on the antigen composition of Covid-19 vaccines released on 13 December 2023.
 
In the WHO Statement, it was noted that SARS-CoV-2 continues to circulate and evolve with important genetic and antigenic evolution of the spike proteins. The spike protein, also known as spike (S) glycoprotein, is the largest major structural protein found in coronaviruses. Its function is to mediate viral entry into the host cell and determines the virus host range (which organisms it can infect) and cell tropism (which cells or tissues it can infect within the organism).
 
The spike protein projects from the surface of the virion and is a major antigen to which neutralizing antibodies are developed. Antibodies against spike proteins are found in patients who have recovered from SARS and Covid-19 and most Covid-19 vaccine development efforts are targeted against the spike proteins, aiming to activate the immune system against the spike protein. Mutations in SARS-CoV-2 spike proteins can result in the virus ability to evade immunity.
 
The WHO Technical Advisory Group on Covid-19 Vaccine Composition (TAG-CO-VAC) meets twice yearly to assess the implications of SARS-CoV-2 evolution for Covid-19 vaccine antigen composition and advise WHO on whether changes are needed to the antigen composition of future Covid-19 vaccines based on their review on the genetic and antigenic evolution of SARS-CoV-2 , the performance and vaccine effectiveness (VE) of currently approved vaccines against circulating SARS-CoV-2 variants during the periods of XBB Omicron lineage circulating, and the implications for Covid-19 vaccine antigen composition. Their last meeting was on 4-5 December 2023.
 
XBB descendent lineages include XBB.1.5, XBB.1.16, EG.5, HK.3 and HV.1 which together accounted for 73% of genetic sequences reported globally but has declined since 2 December 2023. SARS-CoV-2 variant of interest BA.2.86 which made its appearance in July 2023 has 36 amino acid substitutions relative to XBB.1.5, including in key antigenic sites in the spike protein, has been increasing steadily. “Thankfully, these new variants cause mild infections in general, and globally there is a decrease of 18 percent hospitalization and 57 percent in ICU admissions due to these new variants.”
 
WHO Recommendations for COVID-19 vaccine antigen composition
 
Based on the current SARS-CoV-2 evolution and the breadth in immune responses demonstrated by monovalent XBB.1.5 vaccines against circulating variants, the TAG-CO-VAC advises retaining the current Covid-19 vaccine antigen composition, i.e. a monovalent XBB.1.5 as the Covid-19 vaccine antigen.  This monovalent vaccine has now superseded the bivalent vaccine which was introduced in 2022 targeting against the BA.4 and BA.5 Omicron subvariants and the original SARS-CoV-2 virus.
 
This updated Covid-19 vaccine is designed to protect against XBB.1.5 and should also protect against more recent virus variants, including EG.5 and BA.2.86. The US FDA and CDC have approved the updated vaccines by Pfizer-BioNTech and Moderna. The vaccines target XBB.1.5, a subvariant of Omicron that has dominated the world since November 2021 until earlier this year. The CDC said that the updated vaccines should also work against currently circulating variants, many of which are descended from, or are related to, the XBB strain.
 
While SARS-CoV-2 variants have been causing mostly mild illness, it can still lead to hospitalization and death, especially in the elderly and those with comorbidities (immunocompromised people and those with chronic medical conditions such as diabetes or heart disease). Even healthy people can develop Long Covid-19 condition, a condition in which new, continuing or recurring (and sometimes debilitating) symptoms are present for weeks and months after an initial coronavirus infection.
 
“It is important for countries to continue monitoring the emergence of new SARS-CoV-2 variants, and to share the information in real-time with the rest of the world. Any significant change in the genetic and antigenic evolution of SARS-CoV-2 which affect the present vaccine effectiveness of current vaccines will influence the formulation of the next generation of Covid-19 vaccines.”
 
*Emeritus Professor Dato’ Dr. Lam Sai Kit is a Research Consultant, Universiti Malaya And Senior Fellow, Academy of Sciences Malaysia.*