The latest Covid booster will be available soon. Should I get one? Am I eligible?

Australia Therapeutic Goods Administration (TGA) recently approved a recent booster vaccine against Covid-19. The shot was developed by Pfizer and Targets subvariant JN.1 by Omicron.

This is now the fifth version of the COVID vaccines, which are updated regularly to keep up with the rapidly evolving SARS-CoV-2 virus.

But nearly five years into the pandemic, you may be wondering, why do we need yet another type of booster vaccine? And do we still need to take legal highs at all? Here’s what to consider.

Targeting the spike protein

JN.1 booster from Pfizer (and Moderna, although TGA has not approved this stage) is based on mRNA technology. This technology instructs our cells to produce a specific protein – in this case, the SARS-CoV-2 spike, a protein on the surface of the virus that allows it to attach to our cells.

This helps the immune system produce antibodies that recognize the spike protein and prevent the virus from entering our cells.

In response to our enhanced immune response from vaccinations and previous infections (called immune pressure), SARS-CoV-2 has continued to evolve over the course of the pandemic, modifying the shape of the spike protein, making our antibodies less effective.

We’ve been dealing with a soup of Omicron subvariants lately, including the JN.1. Since the detection of JN.1 in August 2023this subvariant of Omicron spawned many further subvariants such as KP.2 (known as FLiRT), KP.3 (known as FLUQE), and XEC.

The spike protein consists of 1273 amino acidskind of like molecular building blocks. Mutations to spike protein change individual amino acids.

Certain amino acids are crucial for neutralizing antibodies to bind to the spike protein. This means the changes could give the virus an advantage over earlier variants, helping it evade our immune response.

Scientists are constantly updating Covid-19 vaccines, trying to keep up with these changes. The better the vaccine’s “spike” matches the spike protein on the surface of the virus trying to infect you, the more protection you can get.

So who should get vaccinated and when?

Updating vaccines to combat mutating viruses is not a recent concept. This has since been the case with the flu vaccine around 1950.

We have become accustomed to the annual flu vaccine in the run-up to winter chilly and flu season. However, unlike the flu, the coronavirus does not follow an annual seasonal cycle. The frequency of waves of Covid-19 infections is variable, with recent waves occurring periodically.

Covid too more portable than the flu, which is another challenge. Although numbers vary, a conservative estimate of the reproduction number (R0 – how many people one person infects) for JN.1 is 5. Compare this to seasonal flu with an R0 of about 1.3. In other words, COVID may be four times more contagious than the flu.

Add to this the immunity resulting from vaccination against Covid (or previous infection) begins to weaken in the following months.

Therefore, for some more vulnerable people, an annual Covid-19 booster is not considered sufficient.

For adults aged 65 to 74a booster dose is recommended every 12 months, but every six months is eligible. For adults over 75, a shot is recommended every six months.

Adults aged 18 to 64 are eligible every 12 months unless they have a severe immune deficiency. Immunodeficiency can cause many conditions, including genetic disorders, infections, cancer, autoimmune diseases, diabetes and lung diseases, as well as organ transplantation. Vaccination is recommended for this group every 12 months, but they are eligible every six months.

Understanding the advice

The JN.1-targeted vaccine should provide good protection against Omicron virus subvariants that are likely to be in circulation in the coming months.

There are a few things that need to happen before JN.1 vaccines are available, such as the Australian Technical Advisory Group on Immunization providing guidance to the government. However, we can reasonably expect that they will be implemented within the next month.

If they reach doctors’ offices and pharmacies before Christmas and you intend to utilize a booster dose, the holiday period may be an additional incentive to buy it, especially if you plan to attend many family and social gatherings in the summer.

In the meantime, XBB.1.5 vaccines remain available. While these are targeted against the earlier Omicron subvariant, they should still provide some protection.

While juvenile, well people may want to wait for updated booster doses, for those who are vulnerable and require vaccination, the decision to hold off on vaccination may be something to consider with your doctor.

Australia’s COVID booster vaccine recommendations, with stronger wording (“recommended” rather than “eligible”) used for vulnerable groups, reflect what we know about Covid-19. People who are older and medically vulnerable are more likely to become very unwell due to the virus.

For juvenile, well people who may be wondering, “Do I even need a COVID booster vaccine?”, it makes sense to get one once a year. Although you are less likely to get Covid, it is possible. Importantly, vaccines also reduce risk developing long Covid.

While COVID vaccines are very good at protecting against severe disease, they do not necessarily prevent infection. Evidence that they reduce transmission has been mixedAND has changed over time.

We realized that vaccination will not free us from Covid-19. But it is still our best defense against severe disease.