Evaluating the Efficacy of Current Vaccines against the Eris Variant - A Recent Update

Introduction

Being intracellular microorganisms, viruses naturally evolve by undergoing mutations (changes in genetic material) and producing diverse variants. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that was responsible for the COVID-19 (coronavirus disease 2019) pandemic is no exception to this phenomenon.

Ever since the emergence of the novel coronavirus (SARS-CoV-2), its viral genome has constantly undergone genetic changes, resulting in several SARS-CoV-2 variants. Global regulatory organizations such as WHO (World Health Organization) and CDC (Centers for Disease Control and Prevention) continuously monitor the emergence of new variants and the efficacy of current vaccines against them. This article investigates one recently evolved COVID-19 variant, EG.5, and the efficacy of available COVID-19 vaccines against it.

What Is the Eris Variant?

Through genomic surveillance conducted by the CDC, a new viral strain (Omicron variant descendant) was detected, which has prevailed since late February 2023, causing a rise in COVID-19 cases in countries like the United States and globally. This new COVID-19 strain is named ‘Eris’ or EG.5.

Some of the important facts about the Eris variant are as follows:

• Eris variant has descended from XBB.1.9.2, sharing a similar spike protein (helps in viral entry into the host cells) with XBB sublineage (subtype) variants.

• Recent reports suggest that the Eris variant does not cause severe infections. However, it is considered more contagious (increased infectivity) and highly transmissible than its sublineage variants.

• The WHO upgraded the status of EG.5 as a variant of interest (VOI) in August 2023. VOI refers to variants that exhibit changes in virus structure and reduced response to existing therapeutic options. VOI strains are less virulent and show limited prevalence but require close surveillance to prevent any major outbreak.

• EG.5 is commonly labeled as the Eris variant, although the name has yet to be officially designated by the CDC or WHO.

What Are the Current Vaccines Available for COVID-19?

Since the advent of the COVID-19 pandemic, scientists and healthcare professionals have been rigorously involved in developing vaccines (substances that prevent infection by inducing immune responses).

The U.S. Food and Drug Administration (FDA) has authorized the following COVID-19 vaccines for current usage:

• mRNA Vaccines - When administered into the human body, these vaccines induce safe protein formation resembling SARS-CoV-2. The immune response is triggered, producing antibodies against these virus-mimicking proteins, thereby protecting against COVID-19 infections. The mRNA vaccine (BNT162b2) recommendations include individuals 12 and older and children six months to five years of age.

• Protein Subunit Vaccines - Coronavirus contains spike proteins that help enter the virus into the host (human body) cells. These spike proteins are modified into vaccines and, when administered, induce antibody production. Adjuvants are added to protein subunits to enhance immune response. These subunit vaccines (nvx-cov2373) are recommended for individuals 12 and older.

• Viral Vector Vaccines - A harmless version of another virus (vector) different from coronaviruses is modified as a vaccine and is used to trigger the immune response. However, this vaccine type has not been used in countries like the United States since May 2023.

• Bivalent COVID-19 Vaccines - These vaccines consist of two mRNA constituents, where the first component is similar to the original COVID-19 strain, and the second is specific to Omicron variants (BA.4 and BA.5 lineages). Presently, only bivalent COVID-19 vaccines are authorized for vaccination in countries like the United States.

How Is the Efficacy of COVID-19 Vaccines Evaluated?

The CDC has formulated the following principles to assess and monitor the effectiveness of COIVID-19 vaccines globally:

• The existing healthcare platforms and database resources are precisely aligned and well-equipped to detect critical clinical outcomes associated with preventable measures in vital populations.

• Periodic recording of data in evaluating new recommendations or modifications related to vaccines.

• High-risk populations such as immunocompromised individuals, elderly adults, and chronic illness patients are under continuous monitoring and supportive care.

• Robust measures like the COVID-19 tracker are used to detect the emergence of new strains and measure vaccine-induced immune responses' potency.

• Vaccine effectiveness is continuously updated in global organizations like the CDC, and various vaccine policies are formulated to maintain the effectiveness of the vaccines against emerging new COVID-19 variants (Eris strain).

What is the Efficacy of Current Vaccines Against the Eris Variant?

The current COVID-19 vaccines are being updated to retain their efficacy against the new EG.5 or Eris variant. According to HHS (U.S. Department of Health and Human Services) reports, these reformulated vaccines would be available in global markets and countries like the United States by September 2023 for human use.

Some of the recent updates on the effectiveness of currency vaccines against Eris variant are given below:

• The virus is similar to XBB.1.9.2 Omicron lineages with a minimal mutation in one of its spike proteins.

• Recent clinical studies suggest that vaccines against XBB lineages are highly effective against the Eris variant.

• EG.5 has a partial antibody (vaccination-induced) neutralizing capacity compared to other coronavirus strains. However, if the individual is fully vaccinated and covers all the booster doses with the currently available vaccines, optimal antibody levels are attained to protect against the Eris variant.

• Booster vaccinations make a person less susceptible to Eris variant infection.

• The bivalent COVID-19 vaccines under current use were found to show reduced efficacy against newly emerged XBB-lineage viruses like Eris variants.

• Hence, the FDA has recommended the manufacturers of mRNA vaccines reformulate the current vaccines to target XBB.1.5 spike protein since an identical amino acid spike sequence is present in EG.5.

• The newly updated vaccines would be monovalent in mRNA composition against XBB.1.5 protein.

• The three-dose booster regime is effective for immunocompromised people even during the Omicron surge. A fourth booster dose is found to be effective for the Eris variant.

• CDC has reported that bivalent COVID-19 vaccines enhance protection against Omicron variants such as XBB and XBB.1.5-related variants. However, these individuals have been previously vaccinated with two to four monovalent COVID-19 vaccines.

• Accelerated clinical trials are conducted to prove the effectiveness of booster doses with existing vaccines against EG.5 variants.

Conclusion

Eris variant, or EG.5, is a newly emerged Omicron variant of SARS-CoV-2 that causes similar clinical symptoms like colds, sore throats, and upper respiratory tract infections. This virus does not cause massive outbreaks, but its transmissible frequency is higher.

Though the efficacy of currently available COVID-19 vaccines is debatable against the Eris variant, authorized reports state that complete coverage with booster doses of existing vaccines offers equivalent protection against Eris variants. Also, global organizations are extensively working to upgrade existing vaccines and increase their effectiveness against Eris variants.