New Vaccines and Drug for Covid

For Prelims: Vaccines and types, Virus Strain and Mutation. Corbevax and Covovax, Molnupiravir, Spike Protein.

For Mains: Mechanism of Vaccine in treating viral infection. Types of Vaccines.

Why in News

Recently, India has approved two Vaccines Corbevax and Covovax, one pill Molnupiravir for treating Covid-19 patients.

Key Points

  • Corbevax - Protein Subunit Vaccine:
    • About:
      • It is a protein subunit vaccine, which means that instead of the whole virus, it uses fragments of it to trigger an immune response.
      • In this case, the subunit vaccine contains a harmless Spike (S) protein.
        • The S protein is a highly glycosylated and large type I transmembrane fusion protein that is made up of 1,160 to 1,400 amino acids, depending upon the type of virus.
        • The S protein plays a crucial role in penetrating host cells and initiating infection.
      • Once the immune system recognises the protein, it produces antibodies to fight a real infection when it happens.
    • Efficacy:
      • Neutralising antibodies against Delta strain indicates a vaccine effectiveness of more than 80 % for the prevention of symptomatic infections based on published studies.
      • In the pivotal Phase III study conducted with an endpoint of immunogenic superiority, it demonstrated superior immune response in comparison with COVISHIELD vaccine when assessed for Neutralizing Antibody (nAb) Geometric Mean Titers (GMT) against the Ancestral-Wuhan strain and the globally dominant Delta variant.
  • Covavax - Recombinant Nanoparticle Vaccine:
    • About:
      • Manufactured by Serum Institute of India (SII), is also a protein subunit vaccine, but uses Recombinant Nanoparticle Technology (RNT). It has been developed by US-based Novavax.
        • Recombinant protein vaccine is another proven approach against Covid-19 virus. This technology teaches the body how to develop immunity against the virus using spike protein.
      • Harmless copies of the spike protein are grown in insect cells; the protein is then extracted and assembled into virus-like nanoparticles.
      • Novavax has used an immune-boosting compound (adjuvant). The same technology is used in HPV and the Hepatitis B vaccine.
    • Efficacy:
      • The vaccine has been evaluated in two Phase 3 trials: a trial in the UK that demonstrated an efficacy of 96.4% against the original virus strain, 86.3% against Alpha and 89.7% efficacy overall.
  • Molnupiravir - Oral Antiviral Drug:
    • About:
      • It works by introducing errors into the virus’s genetic code, which prevents replication.
    • Efficacy:
      • The UK cleared molnupiravir as “safe and effective”.
      • The US did not authorise it for use for longer than five consecutive days, or in patients younger than 18 as it may affect bone and cartilage growth.
      • In India, the recommendation is for treatment of adult Covid patients with oxygen level over 93%, and who have a high risk of progression of the disease, and that the drug be sold by retail only under prescription.

Types of vaccines

  • Inactivated vaccines:
    • Inactivated vaccines use the killed version of the germ that causes a disease.
    • Vaccines of this type are created by inactivating a pathogen, typically using heat or chemicals such as formaldehyde or formalin. This destroys the pathogen’s ability to replicate, but keeps it “intact” so that the immune system can still recognize it. (“Inactivated” is generally used rather than “killed” to refer to viral vaccines of this type, as viruses are generally not considered to be alive.)
    • They usually don’t provide immunity (protection) that’s as strong as live vaccines. So you may need several doses over time (booster shots) in order to get ongoing immunity against diseases.
  • Live-attenuated Vaccines:
    • Live vaccines use a weakened (or attenuated) form of the germ that causes a disease.
    • Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response.
    • The limitation of this approach is that these vaccines usually cannot be given to people with weakened immune systems.
    • Live vaccines are used against: Measles, Mumps, Rubella (MMR combined vaccine), Rotavirus, Smallpox among others.
  • Messenger (m) RNA Vaccines:
    • mRNA vaccines make proteins in order to trigger an immune response. mRNA vaccines have several benefits compared to other types of vaccines, including shorter manufacturing times and, because they do not contain a live virus, no risk of causing disease in the person getting vaccinated.
    • The vaccines are used to protect against: Covid-19.
  • Subunit, Recombinant, Polysaccharide, and Conjugate Vaccines:
    • They use specific pieces of the germ - like its protein, sugar, or capsid (a casing around the germ). They give a very strong immune response.
    • They can also be used on people with weakened immune systems and long-term health problems.
    • These vaccines are used to protect against: Hib (Haemophilus influenzae type b) disease, Hepatitis B, HPV (Human papillomavirus), Pneumococcal disease among others.
  • Toxoid Vaccines:
    • They use a toxin (harmful product) made by the germ that causes a disease. They create immunity to the parts of the germ that cause a disease instead of the germ itself. That means the immune response is targeted to the toxin instead of the whole germ.
    • Toxoid vaccines are used to protect against: Diphtheria, Tetanus.
  • Viral Vector Vaccines:
    • Viral vector vaccines use a modified version of a different virus as a vector to deliver protection.
    • Several different viruses have been used as vectors, including influenza, vesicular stomatitis virus (VSV), measles virus, and adenovirus, which causes the common cold.
      • Adenovirus is one of the viral vectors used in some Covid-19 vaccines being studied in clinical trials.
    • The vaccines are used to protect against:Covid-19