2. COVAXINTM by Bharat Biotech is an indigenous vaccine against Covid-19. Which
type of vaccine is it?
a. Encapsulated mRNA encoding the spike protein
b. Adenovirus expressing the SARS-CoV-2 spike protein
c. Inactivated SARS-CoV-2 virus
d. Modified antisense-RNA targeting the SARS-CoV-2 spike protein

Correct option: c. Inactivated SARS-CoV-2 virus.​​

Introduction

COVAXIN (BBV152) by Bharat Biotech is India’s first indigenous Covid-19 vaccine, developed in collaboration with ICMR–NIV and used widely in the national vaccination programme. For competitive exams, a frequent question asks which type of vaccine COVAXIN is, and understanding the logic behind the options helps in mastering vaccine platform concepts.​

Correct answer explained: Inactivated SARS-CoV-2 virus (Option c)

COVAXIN is a whole-virion inactivated SARS-CoV-2 vaccine, meaning it contains virus particles that have been chemically killed so they cannot replicate or cause disease. These inactivated virions still present the full range of viral antigens to the immune system, triggering antibody and T‑cell responses without the risk of active infection.​

• The virus is grown in Vero cells and then inactivated (for example, with chemicals like beta-propiolactone) to render it non-infectious.​

• An adjuvant (alum plus a TLR7/8 agonist) is added to enhance immunogenicity, a typical strategy for inactivated vaccines.​

• Similar technology platforms are used in classic inactivated vaccines such as those for polio and hepatitis A, which is why COVAXIN is grouped in the “inactivated” or “killed virus” vaccine category.​

This directly matches option c: Inactivated SARS-CoV-2 virus, making it the correct choice.

Why the other options are incorrect

Option a: Encapsulated mRNA encoding the spike protein

Option a describes the platform used by mRNA vaccines, such as the Pfizer–BioNTech and Moderna Covid-19 vaccines, which deliver lipid nanoparticle–encapsulated mRNA coding for the SARS‑CoV‑2 spike protein. After injection, host cells translate this mRNA to produce spike protein, which is then presented to the immune system to induce neutralising antibodies and cellular responses.​

Key points:

• COVAXIN does not contain mRNA; it contains inactivated whole virions.​

• mRNA vaccines are considered genetic vaccines, whereas COVAXIN is a protein-based inactivated vaccine.​

• Therefore, “encapsulated mRNA encoding the spike protein” refers to a different vaccine platform and does not describe COVAXIN.

Hence, option a is incorrect for this question.

Option b: Adenovirus expressing the SARS-CoV-2 spike protein

Option b describes viral vector vaccines, such as Covishield (ChAdOx1 nCoV-19) and Sputnik V, which use a non-replicating adenovirus engineered to carry DNA encoding the SARS‑CoV‑2 spike protein. The adenoviral vector infects host cells, leading to production of spike protein internally and subsequent immune priming.​

Key points:

• Covishield (Oxford–AstraZeneca/Serum Institute) and several other vaccines use this adenovirus vector platform, not COVAXIN.​

• COVAXIN delivers inactivated whole virus, not an adenoviral vector expressing spike.​

• Vector-based vaccines are classified separately from inactivated whole-virion vaccines in Covid-19 vaccine overviews.​

Therefore, option b does not match COVAXIN and is incorrect here.

Option d: Modified antisense-RNA targeting the SARS-CoV-2 spike protein

Option d describes a hypothetical antisense-RNA–based approach, in which engineered RNA molecules would bind to viral RNA, potentially blocking translation of spike protein or promoting degradation. While antisense technologies are used in some therapeutic contexts, they are not the basis of any widely used Covid‑19 vaccine.​

Key points:

• No major approved Covid‑19 vaccine uses “modified antisense-RNA targeting the SARS-CoV-2 spike protein” as its platform.​

• COVAXIN clearly uses an inactivated whole-virion platform, not antisense RNA.​

• This option is likely included to test whether candidates can distinguish real vaccine platforms (mRNA, adenovirus vector, inactivated virus) from distractors.

Thus, option d is incorrect for COVAXIN.

Concept recap: Types of Covid-19 vaccines in this MCQ

For exam preparation, it helps to link each option to a known platform:

• Inactivated whole virus (Correct for COVAXIN)

  • Contains killed SARS-CoV-2 virions that cannot replicate.​

  • Example: COVAXIN (BBV152) by Bharat Biotech.​

• mRNA vaccines (Option a description)

  • Lipid nanoparticle–encapsulated mRNA encoding spike protein.​

  • Examples: Pfizer–BioNTech, Moderna.​

• Adenoviral vector vaccines (Option b description)

  • Non-replicating adenovirus expressing SARS-CoV-2 spike.​

  • Examples: Covishield (ChAdOx1 nCoV‑19), Sputnik V.​

• Antisense-RNA vaccines (Option d description)

  • Conceptual antisense platform, not used in approved Covid‑19 vaccines.​

Remember: For COVAXIN-based MCQs, the key phrase to recall is “whole virion inactivated SARS-CoV-2 vaccine.”​

Exam-focused takeaway

• The correct answer: c. Inactivated SARS-CoV-2 virus.​

• When you see the stem “COVAXIN by Bharat Biotech is an indigenous vaccine against Covid-19. Which type of vaccine is it?”, immediately associate it with inactivated whole-virus platform, not mRNA or adenovirus vector.​