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European Union: first adapted COVID-19 booster vaccines against Omicron Ba.1 subvariant


EMA’s human medicines committee ( CHMP ) has recommended authorising two vaccines adapted to provide broader protection against COVID-19.
Comirnaty Original / Omicron Ba.1 and Spikevax Bivalent Original / Omicron Ba.1 are for use in people aged 12 years and above who have received at least primary vaccination against COVID-19.
These vaccines are adapted versions of the original vaccines Comirnaty ( Pfizer / BioNTech ) and Spikevax ( Moderna ) to target the Omicron Ba.1 subvariant in addition to the original strain of SARS-CoV-2.

Vaccines are adapted to better match the circulating variants of SARS-CoV-2. Adapted vaccines can broaden protection against different variants and are therefore expected to help maintain optimal protection against COVID-19 as the virus evolves.

Studies have shown that Comirnaty Original / Omicron Ba.1 and Spikevax Bivalent Original / Omicron Ba.1 can trigger strong immune responses against Omicron Ba.1 and the original SARS-CoV-2 strain in people previously vaccinated.
In particular, they were more effective at triggering immune responses against the Ba.1 subvariant than the original vaccines.

Side effects observed with the adapted vaccines were comparable to those seen with the original ones and were typically mild and short-lived.

Other adapted vaccines incorporating different variants, such as the Omicron subvariants Ba.4 and Ba.5, are currently under review by EMA.
The clinical data generated with the Original / Omicron Ba.1 bivalent vaccines recommended will support the evaluation and authorisation of further adapted vaccines.

The original vaccines, Comirnaty and Spikevax, are still effective at preventing severe disease, hospitalisation and death associated with COVID-19 and will continue to be used within vaccination campaigns in the European Union ( EU ), in particular for primary vaccinations.
National authorities in the EU Member States will determine who should receive which vaccines and when, taking into account factors such as infection and hospitalisation rates, the risk to vulnerable populations, vaccination coverage and vaccine availability.

The adapted vaccines work in the same way as the original vaccines. Both adapted vaccines work by preparing the body to defend itself against COVID-19.
Each vaccine contains molecules called mRNA which have instructions for making the spike proteins of the original SARS-CoV-2 and the Omicron subvariant Ba.1.
The spike protein is a protein on the surface of the virus which the virus needs to enter the body’s cells and can differ between variants of the virus.
By adapting vaccines, the aim is to broaden protection against different variants.
When a person is given one of these vaccines, some of their cells will read the mRNA instructions and temporarily produce the spike proteins. The person’s immune system will then recognise those proteins as foreign and activate natural defences ( antibodies and T cells ) against them.
If, later on, the vaccinated person comes into contact with the virus, the immune system will recognise the spike protein on its surface and be prepared to attack it. The antibodies and immune cells can protect against COVID-19 by working together to kill the virus, preventing its entry into the body’s cells and destroying infected cells.
The mRNA molecules from the vaccines are broken down shortly after vaccination.

Evidence supporting use of Comirnaty Original / Omicron Ba.1

Comirnaty Original / Omicron Ba.1 can be used in people aged 12 years and older, at least 3 months after the last dose of a COVID-19 vaccine.
The CHMP’s opinion on Comirnaty Original/Omicron Ba.1 is based on 2 studies.

One study in adults over 55 years old who had previously received 3 doses of Comirnaty ( primary vaccination and a booster ) found that the immune response to the Omicron Ba.1 subvariant was higher after a second booster dose of Comirnaty Original / Omicron Ba.1 than after a second dose of the original Comirnaty vaccine ( as measured by the level of antibodies against Omicron Ba.1 ).
In addition, the immune response to the original SARS-CoV-2 strain was comparable for both vaccines.
The study has involved more than 1,800 people, of whom about 300 received Comirnaty Original / Omicron Ba.1 in its final composition.
Further data from a study involving over 600 people aged between 18 and 55 years who had previously received 3 doses of Comirnaty showed that the immune response to Omicron Ba.1 was higher in people who have received a booster with a vaccine containing only Omicron Ba.1 component than in those given a booster with the original Comirnaty vaccine.
Based on these data, it was concluded that the immune response to Omicron Ba.1 following a booster with Comirnaty Original / Omicron Ba.1 in people aged 18 to 55 years would be at least equal to that in people aged over 55.

Further, based on previous data in younger people, it was also concluded that the immune response to a booster dose with Comirnaty Original / Omicron Ba.1 in adolescents would be at least equal to that in adults.

Evidence supporting use of Spikevax Bivalent Original / Omicron Ba.1

Spikevax Bivalent Original / Omicron Ba.1 can be used in adults and adolescents from the age of 12 years, at least 3 months after primary vaccination or a booster dose with a COVID-19 vaccine.

The CHMP’s opinion on Spikevax Bivalent Original / Omicron Ba.1 is based on data from a study involving more than 800 adults aged 18 years and above. The study found that a booster dose of Spikevax Bivalent Original / Omicron Ba.1 has induced a stronger immune response against the SARS-CoV-2 strain and the Omicron subvariant Ba.1 compared with a booster dose of the original Spikevax vaccine.
The study compared the level of antibodies in people previously vaccinated with a primary series and booster dose of Spikevax, and who were given a second booster dose of either Spikevax or Spikevax Bivalent Original / Omicron Ba.1.
It was also concluded that Spikevax Bivalent Original / Omicron Ba.1 could be used as a first booster after primary vaccination and that the immune response has induced by a booster dose of Spikevax Bivalent Original / Omicron in adolescents aged 12-17 years would be at least equal to that in adults, given that previous data with Spikevax have shown a comparable effect. ( Xagena )

Source: EMA, 2022

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