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A new variant of Covid-19, the Omicron variant, is spreading rapidly throughout the world and cases are significantly rising in the UK. With Omicron cases doubling roughly every two days, the Prime Minister has announced the UK is expecting a ‘Tsunami’ of infections in the coming weeks and urged the country to get booster jabs.

Where people have not already received their first or second dose of the Covid vaccines, they too are being urged to come forward and get these now to protect themselves from more severe forms of the disease and help slow down the spread of the virus.

It is still too early to predict exactly what impact this new variant will have on a largely vaccinated population like the UK, but health officials and scientists are concerned that as this variant is even more transmissible than the Delta variant, it will spread rapidly and is expected to quickly become the dominant strain.

In addition, the Omicron variant has many mutations which means it has some significant differences in its spike protein to the original strains of Covid that the vaccines were developed against. As a result, we are still finding out how well our vaccines will protect us from this new variant.

Preliminary data from South Africa, where Omicron was first identified and where numbers are surging, suggest that the Pfizer-BioNTech vaccine offers less protection from infection with Omicron than with previous variants, but it offers good protection from developing severe disease and requiring hospitalisation. This means even vaccinated people are at risk of catching Covid, but hopefully the vaccines will reduce the severity of the disease.

More data is needed to confirm these findings, but the Government is urging everyone to get their vaccines and boost their immunity to prevent a rise in cases of people severely ill with Covid, which would put pressure on an already overstretched NHS.

Scientists have described Omicron as moving extraordinarily fast, so the next few weeks are a race between rising Covid cases and getting the vaccines.

The Government is working to increase the capacity for vaccinations, aiming for 500,000 a day to get everyone vaccinated by the end of the month.

So, if you already have had two vaccines, why is the booster so important? The Omicron variant has many mutations compared with the original strains of virus the vaccines were developed against. This has reduced the vaccines’ ability to protect us from catching this variant, but there is enough overlap between the viruses that the vaccines should protect us from getting seriously ill.

This is an important point; people should not assume vaccines mean they do not catch the virus and get ill or transmit the virus to other people. You can still potentially catch Covid even when fully vaccinated – the vaccines will help lessen the severity of the disease, thus reducing the risk of hospitalisation and death. Data have suggested that antibodies from people who have had two doses of a Covid vaccine could not combat the Omicron variant, but people who had received boosters could.

The booster jab is not just effectively more of the same vaccine with the same result – what it does is challenge the immune system with the virus again and this repeated challenge elicits an immune response that is bigger, broader and more memorable than the previous ones.

When your body encounters a new virus for the first time, it has to learn how to deal with it and clear it from the body – if it cannot, the person will fall ill and eventually could die. The immune system has a range of ways to fight infections and is a very complicated and integrated system that involves several cell types.

The Covid vaccines give the body just a small part of the virus, the protein spike, to deal with and after your first jab, the body will produce antibodies that can recognise and bind to this part of the virus, neutralising it, so it cannot enter and infect cells and also alerting other cells that this ‘invader’ needs to be dealt with and destroyed.

Having been through the process once, the body retains a ‘memory’ of it so when it encounters the virus again (e.g., with a booster dose) it will produce a bigger, quicker and stronger response, with a higher number of antibodies each time.

Every time the body encounters the virus or a vaccine, it will trigger another round of antibody evolution within the immune system, such that new antibodies are made that attach themselves more firmly to the virus, so with each dose, the antibody response becomes more refined and improved. Even though Omicron has mutations, it is still related to the original virus and the antibodies should be able to bind to it.

The booster dose will mean antibody levels are boosted and refined, and these should stay at high levels within the body for several months, offering a good level of protection from the disease.

Early laboratory tests have shown that a third dose of the Pfizer vaccine resulted in a 25-fold increase in neutralising antibodies that attack Omicron, a similar level of protection that two doses gave against the original strain.

Often over time, antibody levels fall, and you are at risk of re-infection. Although the body should be able to launch an effective immune response again, this will take time and the person may experience some illness.

But the more times your immune system is ‘challenged’ with the virus, the longer lasting the immune memory is, which is why people are being urged to get their boosters now ahead of the new wave of Omicron infections.

Given that we are going to have to learn to live with Covid, many are asking, will we need to keep getting booster vaccines? As yet, there is no scientific consensus on this, but some scientists are suggesting we might need to have an annual vaccine, like the flu vaccine, to protect us from new emerging variants.

While Covid may spread in unvaccinated parts of the world, there is always the risk of new variants arising that can evade the vaccines, requiring new boosters to be developed.

Thus, how quickly Covid can be brought under control throughout the world through vaccination is important as mutations arising in unvaccinated populations will always pose a risk as we have seen how fast Covid can spread globally. The supply of vaccines to poorer nations is another issue that also needs to be addressed in the continuing fight against Covid.

Rachel Kayani