Real-world study in India finds COVISHIELD vaccine safe and effective

New research led by Naresh Trehan of Medanta-The Medicity in India found the COVISHIELD (ChAdOx1 nCoV-19 Corona Virus Vaccine) vaccine produced an immune response from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) two weeks after vaccination with limited side effects.

While national vaccination campaigns officially began on January 16, 2021, limited access has slowed the rollout. The COVISHIELD vaccine is produced by the Serum Institute of India and could help with the rising COVID-19 cases in India and prioritizing vaccines for frontline workers and at-risk groups.

The researchers write:

“The rollout of vaccines in several parts of the world is being hailed as a solution to the crisis. With newer and more virulent serotypes on the horizon and limited vaccine available, evaluation of safety and immunogenicity is critical for rationalization of vaccine use in public health.”

The study “A Real-World Evaluation of the safety and immunogenicity of the Covishield vaccine, ChAdOx1 nCoV- 19 Corona Virus Vaccine (Recombinant) in Health Care Workers (HCW) in National Capital Region (NCR) of India: A preliminary report” is available as a preprint on the medRxiv* server, while the article undergoes peer review.

Study design and enrollment

The study occurred in a hospital in the National Capital Region of Delhi, where 6,962 healthcare workers registered for vaccination. Researchers excluded healthcare workers who had already taken part in a COVID-19 trial, had received immunoglobulins or convalescent plasma within three months of being administered the vaccine or were not able to receive the vaccine for other health reasons.

Participants completed a baseline questionnaire on socio-demographics, health information, and history of COVID-19 infection. They also donated 3 ml of blood on the day of vaccination and 14 to 16 days after receiving their first dose. Every person filled out a daily diary to record any adverse events and the severity of the events. A phone line was also available to document any unsolicited adverse vaccine-related reactions, such as vaccine-associated enhanced respiratory disease and symptomatic COVID-19 infection.

Laboratory analysis of serum measured Immunoglobulin G (IgG) antibodies specific to the SARS-CoV-2 spike protein.

Seropositivity observed after vaccination

The serostatus of healthcare workers rose from 48.2% at baseline to 79% two weeks after receiving the first vaccine dose. Healthcare workers who had a history of COVID-19 infection had an even greater seropositivity rate at 98.2%. People considered seropositive at baseline showed a further boost in seropositivity than people considered seronegative at baseline.

Based on the results, the researchers suggest having prior exposure to SARS-CoV-2 may prime the immune system to produce an antibody response, with the first vaccine dose acting more like a booster. This confirms evidence of people with a prior infection possibly not needing a second vaccine dose.

COVISHIELD vaccine shows a good safety profile

Side effects were often reported two days after receiving a vaccine, and all had resolved soon after. People older than 50 experienced less severe reactions.

The most common side effects following vaccination were pain at the injection site and soreness. About 62.7% of healthcare workers reported pain, while 24.1% reported soreness in their daily diary cards.

Systemic adverse events reported in the daily diary cards included fever (48.4%), headache (43.4%), myalgia (38.4%), fatigue (33.4%), joint pain (27.0%), and nausea (16.0%).

There were no severe adverse events that required hospitalization or a trip to the emergency room.

Participants completed a survey on side effects, and 66% had reported at least one symptom after vaccination. The most prevalent were tiredness (45%), myalgia (44%), fever (34%), headache (28%), local pain at the injection site (27%), joint pain (12%), nausea (8%) and diarrhea (3%).

There were no reports of vaccine-associated adverse events of particular interest, including vaccine-associated enhanced respiratory disease or symptomatic COVID-19 infection in the first 14 days of the study.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Jocelyn Solis-Moreira

Written by

Jocelyn Solis-Moreira

Jocelyn Solis-Moreira graduated with a Bachelor's in Integrative Neuroscience, where she then pursued graduate research looking at the long-term effects of adolescent binge drinking on the brain's neurochemistry in adulthood.


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