COVID-19 Vaccines

COVID-19 Vaccines: How effective are they in the real world?

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By Apollo 24/7, Published on- 12 March 2021, Updated on - 18 October 2022

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Starting December 2020 and early this year, manufacturers of the top COVID-19 vaccines began publishing their clinical efficacies from the phase 3 trials. All the front runners reported high efficacy rates and were provided emergency approvals. However, the attention has now shifted to another important aspect – about how effective these vaccines are proving to be in the real world as they get rolled out to the public globally.

Recently, several scientific studies have been released highlighting the difference between the clinical efficacy of some of the top COVID-19 vaccines and their real-world effectiveness. We explore the difference between vaccine efficacy and vaccine effectiveness and share insights about the effectiveness of some of the major COVID-19 vaccines.

Understanding vaccine efficacy and effectiveness

Vaccine efficacy and vaccine effectiveness are two terms that are often used interchangeably but have a subtle difference.

  • Vaccine Efficacy - It is the percentage reduction of disease incidence in a vaccinated group of people compared to an unvaccinated group, under the most ideal conditions, as part of a randomized controlled trial.
  • Vaccine Effectiveness - It refers to the ability of a vaccine to prevent a disease or infection in “real world” settings. It is measured once a vaccine has been approved for use in humans via observational studies

According to epidemiologists, the efficacy of a vaccine in clinical trial conditions may not always translate into equivalent vaccine effectiveness in the real world.

Comparison of vaccine efficacy and effectiveness of major COVID-19 vaccines

Oxford/AstraZeneca vaccine (Covishield in India)

Developed by the University of Oxford, UK, and British-Swedish biopharmaceutical firm AstraZeneca, this vaccine is being license manufactured in India as ‘Covishield’ by the Pune-based Serum Institute of India. Covishield is one of the two COVID-19 vaccines that are currently approved for immunization in India.

As per the first interim analysis of the phase 3 trial data, the Oxford/AstraZeneca vaccine was shown to have an average efficacy of 70%. Until recently, not much was known about the vaccine’s effectiveness in real-world scenarios. However, crucially important data about the real-world performance has started to come in and they point to encouraging outcomes in people who have received this vaccine.

  • Recently, a study titled “Assessing the Effectiveness of BNT162b2 and ChAdOx1nCoV-19 COVID-19 Vaccination in Prevention of Hospitalisations in Elderly and Frail Adults: A Single Centre Test Negative Case-Control Study” was released. The study noted that the first dose of the Oxford/AstraZeneca vaccine is 80.4% effective in reducing hospitalizations due to COVID-19 infection in elderly adults.
  • A study called “Early effectiveness of COVID-19 vaccination with BNT162b2 mRNA vaccine and ChAdOx1 adenovirus vector vaccine on symptomatic disease, hospitalizations, and mortality in older adults in England” has found that in people aged 70 years and above, one dose of the Oxford/AstraZeneca vaccine was 60% effective in preventing COVID-19 from 28 to 34 days post-vaccination. The figure increased to 73% from day 35 onwards.
  • Another study called “Effectiveness of First Dose of COVID-19 Vaccines Against Hospital Admissions in Scotland: National Prospective Cohort Study of 5.4 Million People” has found that the risk of hospitalization was reduced by up to 94% after one dose of the Oxford/AstraZeneca vaccine at 28-34 days post-vaccination.
  • Emerging scientific evidence suggests that the vaccine can also significantly reduce the transmission of the virus. According to the study “Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine, one dose of the vaccine can cut transmission of the SARS-CoV-2 virus by 67%.

Pfizer-BioNTech Vaccine

The vaccine, jointly developed by the US pharma company Pfizer and German biotech company BioNTech, was the first COVID-19 vaccine to be given emergency approval in the world. According to the first interim analysis of the phase 3 trial data, the vaccine had a 95% efficacy rate.

The clinical efficacy of the vaccine has been supported by some observational studies in the real world. According to a large study conducted in Israel, two doses of the vaccines lowered symptomatic COVID-19 by 94% across all age groups after 1 week of getting the second dose. It also reduced the risk of severe illness by 92%, in the real world.

What about the real-world effectiveness of other COVID-19 vaccines?

As of Mar 2021, the real-world effectiveness of other COVID-19 vaccines have not yet been published. However, based on the interim analyses of their phase 3 trial data, their efficacy rates are:


Efficacy rate

Sputnik V (Gam-COVID-Vac)


Novavax (NVX-CoV2373)


Johnson & Johnson (JNJ-78436735)

66% (symptomatic), 85% (severe)

Bharat Biotech (COVAXIN)


As a result, not much is known yet about the real-world effectiveness of these vaccines in preventing transmission, hospitalization, and deaths. This could be due to the following two reasons:

  • Lack of large-scale introduction
  • Unavailability of data from observational studies

Despite the lack of data highlighting the real-world effectiveness of some of the vaccines, it is important to note that one should still get these vaccines once they are available to them. Real-world effectiveness data generally starts becoming available after it is introduced in the community and enough people have received the vaccine.

It is important to note that all approved vaccines have passed rigorous clinical trials and scrutiny of the drug regulatory authorities and can be trusted to offer protection against COVID-19. It is hoped that the other vaccines will soon start reporting encouraging real-world effectiveness data.

Status of COVID-19 immunization in India

In India, the COVID-19 vaccination programme has progressed at a rapid rate. As of 11 March 2021, more than 25.6 million people have received either of the two approved COVID-19 vaccines. Currently, only healthcare professionals, frontline workers, people aged 60 and above, and those aged between 45 to 59 years with certain comorbidities are eligible to receive COVID-19 vaccines in India.

The government has designated these groups as priority beneficiaries owing to their higher risk of contracting the infection, hospitalization, and mortality. Therefore, it is important for these people to register themselves for vaccination.

How Apollo is helping its customers with the COVID-19 vaccination

Apollo is geared up to support the world's largest vaccination drive, in the safest manner possible by following all government-issued guidelines and regulations. Apollo is offering vaccinations for specified groups - ages 60+ and 45+ with comorbidities currently - at low, government-approved prices. Apollo is also enabling COVID-19 vaccinations for various corporates and residential welfare associations.

Apollo’s 24|7 app offers a spectrum of vaccination services. Customers can use it to:

  • Book and schedule a COVID-19 vaccination in 3 easy steps
  • Speak with a COVID doctor for any queries (a complimentary service)
  • Consult specialist doctors before and after vaccination
  • Access verified and trusted COVID-19 FAQs and Articles

It is important to note that the battle against the COVID-19 pandemic can only be won when each of us does our part – take the vaccine when it is our turn.


COVID-19 Vaccines

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