COVID-19 vaccines are one of the most significant achievements in modern medicine. Developed in record time through unprecedented global scientific collaboration, they have played a central role in reducing severe illness and deaths from the coronavirus pandemic. This guide explains how they work, the main types, and what the science says.

How Do COVID-19 Vaccines Work?

All COVID-19 vaccines work by training your immune system to recognise and fight the SARS-CoV-2 virus without you having to get infected first. They introduce your body to a part of the virus — or instructions to make that part — so your immune system can build a memory response. If you encounter the real virus later, your body can respond quickly and effectively.

The Main Types of COVID-19 Vaccines

1. mRNA Vaccines (Pfizer-BioNTech, Moderna)

These vaccines use messenger RNA (mRNA) — a set of genetic instructions — to tell your cells how to make the spike protein found on the surface of the coronavirus. Your immune system recognises this spike protein as foreign, mounts a response, and builds antibodies. The mRNA itself breaks down within days and never enters the cell nucleus or interacts with your DNA.

2. Viral Vector Vaccines (Covishield / AstraZeneca, Sputnik V, Johnson & Johnson)

These use a modified, harmless virus (the vector) to carry genetic instructions for making the coronavirus spike protein into your cells. Covishield, manufactured by the Serum Institute of India, was one of the most widely administered vaccines in India during the pandemic.

3. Inactivated Virus Vaccines (Covaxin, Sinopharm)

These use a killed version of the actual coronavirus. Your immune system learns to recognise the inactivated virus and prepares a defence. Covaxin, developed by Bharat Biotech and ICMR, was India’s first indigenously developed COVID-19 vaccine and received WHO Emergency Use Listing in 2021.

4. Protein Subunit Vaccines (Novavax / Covovax)

These contain harmless pieces of the spike protein itself, along with an adjuvant to boost the immune response. They use a more traditional vaccine-making approach similar to existing hepatitis B and whooping cough vaccines.

Are COVID-19 Vaccines Safe?

COVID-19 vaccines were reviewed by regulatory agencies in multiple countries — including India’s Central Drugs Standard Control Organisation (CDSCO), the US FDA, the European Medicines Agency, and the WHO — before receiving authorisation for emergency use. All vaccines authorised globally underwent rigorous clinical trials involving tens of thousands of participants.

Like all vaccines, COVID-19 vaccines can cause mild, temporary side effects such as a sore arm, fatigue, or low-grade fever — signs that your immune system is responding. Serious side effects are rare and are continuously monitored through post-market surveillance systems.

How Effective Are COVID-19 Vaccines?

Vaccine effectiveness varies by type and the circulating variant. During the original and Delta wave phases, mRNA vaccines showed efficacy rates of 90–95% against severe disease. Covishield showed approximately 70–90% efficacy depending on dosing interval. Covaxin demonstrated around 77–78% efficacy against symptomatic disease in Phase 3 trials.

All authorised vaccines consistently showed high effectiveness against hospitalisation and death, which remains their most critical public health goal.

India’s Vaccination Drive

India launched one of the world’s largest vaccination campaigns in January 2021, initially administering Covishield and Covaxin. The country administered over 2 billion doses, making it one of the most vaccinated nations by volume. Additional vaccines including Corbevax and Covovax were later added to India’s national immunisation programme.

Where to Get Accurate Information

For the most current guidance on COVID-19 vaccines — including booster recommendations and any new variants — always refer to trusted sources:

• Ministry of Health & Family Welfare, India: mohfw.gov.in
• World Health Organisation: who.int
• ICMR: icmr.gov.in

This article is for general information purposes only. Always consult a qualified healthcare provider for personalised medical advice.