Bivalent vaccine – SOCHINF
The SARS-CoV-2 pandemic brings with it the viral evolution characteristic of RNA viruses, with higher mutation rates and thus the emergence of variants. The humoral and cellular adaptive immune response is stimulated by both disease and vaccination. The adaptive humoral response includes specific antibodies against the spike protein epitopes of SARS-CoV-2 with a neutralizing ability, being the primary site of action of this type of immune response.
A well-defined humoral response correlates with a decrease in infection, and thus a cellular response to a decrease in severe illness and death, as shown in the following graph (on the left).
There are about 300 vaccines in preclinical or clinical studies and 10 of them have been approved by the World Health Organization. This saved more than 20 million lives in the first year of implementation.
As the epidemic progresses, viral replication generates mutations and ergos, new variants. Vaccines designed for the ancestral virus (Wuhan/Hu-1) lose their efficacy, and this is secondary to the change of epitopes where the antibodies bind. The emergence of the first D614G mutation (increased viral fitness) and later the alpha (B.1.1.7), beta (B.1.351), gamma (p. 1) and delta (B.1.617.2) variants until the current omicron (B.1.1.529) caused the accumulation of mutations from beta with 4 mutations to the omicron with more than 50 mutations (30 of which are in the spike protein), resulting in significant escape of the SARS-CoV-2 variant from the omicron into antibody neutralizing factors resulting from vaccines produced with the progenitor virus. In addition, ómicron for its part produced sub-variables (BA.1, BA.1.1, BA.2, BA.2.12.1, BA.4 and BA.5).
Therefore, the need for a vaccine that has a better adaptive immune response to the omicron variant becomes apparent. For this reason, the Pfizer (Clinicaltrials.gov, NCT05472038) and recent (Clinicaltrials.gov, NCT05249829) vaccines, both were developed on the Spike mRNA platform for ancestral virus and omicron virus (BA.1).
The modern inoculum (mRNA-1273.214) increased equilibrium geometric mean (GMT) titers against omicron 8-fold at baseline levels and 4.7-fold for progenitor virus on day 29 of follow-up. For Pfizer (Pfizer-BioNTech COVID19 injectable 15/15 bivalent vaccine), the increase in neutralizing geometric mean (GMT) titers of the omicron was 9.1-fold over baseline at 28 days for the bivalent vaccine group.
The safety profile of the described bivalent vaccines, which show the same or less adverse effects than monovalent vaccines from the same platform (mRNA) already authorized during the epidemic, is highlighted, with puncture site pain, headache and fatigue being the most common symptoms. often mentioned.
Due to the described results, it was approved by the ISP for use as a boost on September 30, 2022 with the permission of Section 99 of the Health Code, pursuant to Exemption Resolution No. 4307 and No. 4306 respectively. On this occasion, the promotion targets the following segments of the population (target coverage 80%):
- health workers
- immunity
- People with chronic diseases
- Adults from 60 years old
The vaccination schedule for bivalent vaccines is a booster for those who received an initial schedule of 16 weeks apart or at least one dose of the booster 24 weeks apart from the last dose received.
Finally, a new tool has been added to combat SARS-CoV-2 in the most dangerous segments of the population of our country.
References:
- Article review: Covid-19 Vaccines – Immunology, Variants, and Boosters Dan H. Barouch, MD, Ph.D. Engel Gem Made 2022; 387: 1011-20. doi: 10.1056/NEJMra2206573
- Bivalent omicron-containing booster vaccine against Covid-19 N Engl J Med 2022; 387: 1279-91. doi: 10.1056/NEJMoa2208343
- A study to identify new COVID-19 RNA vaccine candidates as a booster dose in healthy individuals who have had a COVID-19 vaccine.
- Technical guidelines for booster doses with a bivalent SARS-CoV-2 vaccine. Exempt Resolution 1425. October 6, 2022.
