On the one hand, where the air of North India including Delhi-NCR has become poisonous due to terrible air pollution and the respiratory crisis is deepening, another big news is coming about health. Australia's Therapeutic Goods Administration (TGA) recently approved a new Covid booster (vaccine). This vaccine has been developed by Pfizer. It targets the Jn.1 subvariant of Omicron.
This is the fifth version of the Covid vaccines, which has been updated regularly to combat the rapidly mutating SARS-CoV-2 virus. But almost five years after the pandemic, you might be wondering, why do we need another kind of Covid booster? And do we still need boosters? Here are the things to consider.
Targeting the spike protein is based on mRNA technology based on Pfizer's JN.1 booster (and Moderna's, but TGA's, but not approved at this stage). It instructs our cells to make a specific protein — in this case the spike of SARS-CoV-2, a protein on the surface of the virus that allows it to attach to our cells. It helps the immune system produce antibodies that recognise the spike protein and prevent it from entering our cells.
In response to our strong immune responses from vaccination and previous infections (called immune pressure), SARS-CoV-2 has continued to mutate during the pandemic, it has modified the shape of its spike protein so that our antibodies become less effective.
Recently, we have seen several sub-variants of Omicron, including JN.1. Since JN.1 was first detected in August 2023, this Omicron sub-variant has spawned several other sub-variants, such as KP.2 (known as Flirt), KP.3 (known as Fluke) and ZEC.
The spike protein is made up of 1,273 'amino acids', which are somewhat like molecular building materials. Mutations in the spike protein change individual amino acids.
Certain amino acids are important for antibodies to bind to the spike protein. This means the changes can give the virus an edge over an earlier variant, helping it evade our immune response.
Scientists keep updating the Covid vaccine in an effort to keep pace with these changes. The better the "spike" of the vaccine matches the spike protein on the surface of the virus trying to infect you, the better protection you are likely to get.
So who should take the vaccine and when
Updating vaccines to combat virus mutations is not a new concept. This has been happening for flu vaccines since around 1950.
We are used to getting the flu vaccine every year before winter and flu season. But, unlike influenza, Covid has not yet arrived in this annual seasonal cycle. The frequency of waves of Covid infection has been fluctuating, with new waves coming from time to time.
Covid is even more contagious than the flu, which presents another challenge. Although the numbers vary, a conservative estimate of the reproduction number (RO i.e. how many people a person will infect) for JN.1 is five. Compare this to seasonal flu which has an RO of about 1.3. In other words, Covid can be four times more contagious than the flu.
Immunity from Covid vaccination (or previous infection) also begins to decline in the months that follow. Therefore, an annual Covid booster is not considered sufficient for some of the more vulnerable.
A booster is recommended every 12 months for the elderly aged 65 to 74 years, but they are eligible for a dose every six months.
