Regulators in the EU, the UK and the US have approved vaccines specifically designed to help the body to combat the omicron variant of SARS-CoV-2 ‒ the virus that causes Covid-19.
The first generation of Covid-19 vaccines approved by regulators targeted the original virus. The latest booster doses are ‘bivalent’, meaning they can protect against two forms of the virus.
Vaccines approved by European regulators in early September protect against the original SARS-CoV-2 virus and omicron BA.1, while another updated vaccine against the original virus and omicron BA.4/5 has now also been given the green light.
‼️ EMA has recommended authorising a new adapted COVID-19 #booster vaccine.
— EU Medicines Agency (@EMA_News) September 12, 2022
This additional adapted version of Comirnaty targets the #Omicron subvariants BA.4 and BA.5 and is for use in vaccinated people aged 12 and over.#AdaptedVaccines #COVID19
👉 https://t.co/zVj9ceWHAu pic.twitter.com/NadSqr9hlF
Vaccines that target more than one virus are not new. The annual flu vaccine is updated annually to protect against the three or four strains of influenza virus that experts consider most likely to cause flu in winter time.
Transatlantic differences
There were subtle differences in the approach taken by experts on either side of the Atlantic as preparations begin for an anticipated increase in Covid-19 infections this winter.
The UK Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency (EMA) first approved vaccines targeting Covid-19 omicron BA.1. This highly contagious variant was first identified in November, thanks to diligent disease surveillance and virus gene sequencing in South Africa.
Since then, several newer Covid viruses have emerged which are similar to omicron BA.1 Two variants known as BA.4 and BA.5 have become particularly dominant this summer, with the latter continuing to cause most cases globally. As a result, vaccine makers have again reworked their vaccines and submitted data on BA.4 and BA.5 vaccines for regulators to review.
In the US, the Food and Drug Administration (FDA) approved vaccines targeting BA.4/5 in August, based primarily on data from studies looking at vaccines against BA.1. EU regulators took a few more weeks to pore over the date but have now authorised them for use.
Regulators are content that the viruses ‒ and therefore the vaccines ‒ are sufficiently similar to allow experts to reasonably conclude that a BA.1 and a BA.4/5 vaccine will be similarly safe and effective against severe disease. Regulators also have a very large volume of safety data showing how the original Covid-19 vaccines performed in the real world.
Which omicron vaccine should you have?
Vaccines are now approved that protect against
(a) the original virus only
(b) the original virus and omicron BA.1 and
(c) the original virus and BA.4/5.
That may sound complex, prompting the question: which Covid vaccine should I have this winter?
The answer, however, is simple: The best Covid vaccine is the one you are offered.
All authorised Covid booster vaccines remind the natural immune system of the virus, helping it to respond to infection. Omicron vaccines provide broader protection against current and emerging omicron variants.
The EMA says preliminary data indicate that the immune response induced by the approved BA.1 adapted vaccines goes beyond the selected strains and covers other Omicron subvariants such as BA.2, BA.2.75 and BA.5.
The Director of ECDC, Dr Andrea Ammon, stressed the importance of vaccines in the fight against the COVID-19 pandemic. ‘With the newly authorised adapted COVID-19 vaccines, Member States will now have a wider range of choices to roll out autumn/winter COVID-19 immunisation campaigns aimed at protecting most vulnerable groups and boost their immunity against most recent emerging variants,’ she said.
‘The authorisation of the first two adapted vaccines is an important step in our ongoing fight against the pandemic’ said EMA’s Executive Director, Emer Cooke. ‘We have a virus that evolves quickly and unpredictably. It is important for the EU to have a broad range of vaccines that are updated with respect to their composition’.
Omicron vaccines protect against severe disease
At a recent World Health Organisation briefing, Dr Maria Van Kerkhove, Technical Lead, COVID-19 Response, said BA.5 is dominant around the world, except in India where the BA.2.75 variant is more common. ‘The virus continues to change. We expect that there will be more variants of concern as the virus continues to evolve,’ she told the meeting. ‘Vaccines prevent severe disease. It’s really important to have the vaccine when it is recommended to you.’
The SARS-CoV-2 virus has changed more frequently and substantially than anticipated earlier in the pandemic. It was once hoped that there would be no need to update the vaccines once they were developed, as is the case with vaccines against many other diseases. For example, measles vaccines do not need to be updated.
Dr Kanta Subbarao, Director of the WHO Collaborating Centre for Reference and Research on Influenza, Melbourne, said there have been a large number of changes in the virus’s signature spike protein ‒ which is targeted by vaccines. ‘When you have changes in the spike protein, the virus can evade the protective response from vaccines or prior infection,’ she told the WHO webinar.
However, Dr Subbarao noted that all approved Covid-19 vaccines still provide some protection against severe disease, even though there appears to be limited success in preventing infection entirely.
‘We have observed that currently licensed vaccines have continued to perform very well in protecting against severe illness and death irrespective of what variant we are seeing ‒ including omicron,’ she said. ‘We would anticipate that bivalent vaccines against omicron BA.1 and BA.4/5 will broaden immunity.’
The question now is whether this process of updating and approving adapted Covid-19 vaccines will become an annual occurrence, as is already the case for influenza vaccines.
