Understanding the Shift from Bivalent to Monovalent Vaccines: A Closer Look at the Latest COVID Boosters

Understanding the Shift from Bivalent to Monovalent Vaccines: A Closer Look at the Latest COVID Boosters

As the COVID virus continues to evolve, our vaccine response must adapt to provide better protection. Starting from December 11, Australians will have access to new vaccines that offer improved efficacy against currently circulating strains of SARS-CoV-2, the virus responsible for COVID-19.

The latest development in the vaccine landscape is the introduction of “monovalent” booster vaccines. These new vaccines, such as Pfizer’s monovalent vaccine for individuals aged five and older and Moderna’s monovalent vaccine for those aged 12 and older, have a single target and are specifically designed to address the latest subvariant of the Omicron variant known as XBB.1.5 or Kraken.

To understand the shift from bivalent to monovalent vaccines, we must first grasp the initial concept of the vaccines. The original COVID vaccines were “monovalent,” targeting only the original viral strain. However, as the virus mutated, new variants emerged, leading to immune evasion where the original vaccines failed to provide sufficient immunity. The introduction of bivalent vaccines was a response to these mutations, targeting the early Omicron subvariant BA.1 alongside the ancestral strain.

Despite the bivalent vaccines’ initial effectiveness, the Omicron variant continued to evolve, resulting in further immune escape and subsequent waves of transmission. To keep up with the evolving virus, the vaccines underwent another update in early 2023, targeting the ancestral strain and the subvariants BA.4 and BA.5.

Now, with the emergence of the XBB.1.5 or Kraken subvariant, the latest booster vaccines have returned to a monovalent approach. This means they only target the specific subvariant, as immunity against the original strain is no longer required since it no longer infects humans. These monovalent vaccines have been approved by regulatory authorities in various countries, including the United States, Europe, Canada, Japan, Singapore, and Australia.

Evidence for the efficacy of these new monovalent vaccines comes from research submitted by Pfizer and Moderna to regulatory bodies like the Therapeutic Goods Administration (TGA). Lab studies, human trials, and observations in mice have shown that the updated vaccines generate good levels of antibodies, surpassing previous vaccines and effectively countering multiple emerging variants, including EG.5 or Eris.

In conclusion, the shift from bivalent to monovalent vaccines represents the ongoing battle to combat the evolving COVID virus. By targeting the latest subvariant, these new boosters strive to provide better protection and adapt to the changing landscape of viral mutations. It is important for eligible individuals to consider getting vaccinated to enhance their immunity against COVID-19 and contribute to curbing the spread of the virus.

Frequently Asked Questions (FAQ)

1. Who is eligible for the new monovalent booster vaccines?

The new monovalent booster vaccines are available to eligible individuals aged five years and older for Pfizer’s vaccine and 12 years and older for Moderna’s vaccine.

2. How do monovalent vaccines differ from earlier ones?

Monovalent vaccines have a single target and specifically address the latest subvariant of the Omicron variant known as XBB.1.5 or Kraken. Earlier bivalent vaccines targeted multiple strains, including the ancestral strain and earlier subvariants.

3. Do the new monovalent vaccines work?

Evidence from research and clinical trials suggests that the new monovalent vaccines produce good levels of antibodies and effectively counter multiple emerging variants, including EG.5 or Eris. This indicates their efficacy in providing protection against COVID-19.

4. Are the new monovalent vaccines safe?

Regulatory authorities, such as the Therapeutic Goods Administration (TGA), have approved the new monovalent vaccines after evaluating their safety and efficacy. It is important for individuals to consult with healthcare professionals and follow official guidance regarding vaccination decisions.

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