THE benefits of vaccination in preventing Covid-19 far outweigh the risks of rare side effects from vaccination say experts.
Covid-19 vaccine safety is being debated once again given issues related to the AstraZeneca vaccine and its reported rare side effects, which has raised concerns among vaccine recipients.
The risk of serious side effects associated with the AstraZeneca vaccine has been documented but occurrence has been rare, says Malaysian Medical Association president Dr Azizan Abdul Aziz.
The Health Ministry was transparent in providing the public with sufficient information and data on the efficacy, safety and risk of side effects of all Covid-19 vaccines available at that time when we were at the height of the pandemic, she says.
"We believe the government, at that time, had carried out all necessary steps to ensure the vaccines were effective and met our country's safety requirements before it was approved for use."
Moreover, healthcare is highly regulated, adds Dr Azizan.
As part of the standard operating procedures (SOPs) for carrying out vaccination, all Adverse Events Following Immunisation (AEFI) cases were reported to health authorities via a system to monitor for issues.
"Covid-19 vaccines may have been developed fairly quickly but not without sufficient research."
Morever, the benefits of the vaccines far outweighed the possible rare side effects at a time when mortality and morbidity of Covid-19 infection was very high, she adds.
Monash University Malaysia Associate Professor (molecular virology) Dr Vinod RMT Balasubramaniam agrees that while the development timeline for Covid-19 vaccines was indeed expedited due to the urgent global need, rigorous safety and efficacy assessments were conducted throughout the vaccine development process.
"Covid-19 vaccines saved countless lives," says Vinod, who is leader of Infection and Immunity Research Strength at the Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia.
"I strongly object to the notion that there are conspiracy theories or government cover-ups regarding the safety of these approved vaccines," he adds.
A study published in the journal 'Lancet Infectious Diseases' found that between Dec 8, 2020, and Dec 8, 2021, vaccinations prevented around 14.4 million Covid-19 deaths in 185 countries and territories.
Vinod says Thrombosis with Thrombocytopenia Syndrome (TTS), which has been linked to the AstraZeneca vaccine, is an exceptionally rare immunological reaction that leads to clots in certain locations such as the brain and elsewhere.
While the exact mechanism behind TTS is still being studied, researchers believe it involves an immune response triggered by the adenovirus vector used in the vaccine.
Vinod says the AstraZeneca vaccine uses a weakened version of a common cold virus (adenovirus) to deliver genetic material from the SARS-CoV-2 virus into our cells.
This genetic material instructs cells to produce a protein found on the surface of the coronavirus, stimulating an immune response.
"In some individuals, the adenovirus vector triggers an immune response that leads to the production of antibodies against not only the coronavirus spike protein but also against a protein called platelet factor 4 (PF4), which is involved in blood clotting," explains Vinod.
These antibodies can bind to PF4, causing platelets (cell fragments in the blood that help with clotting) to become activated. This activation leads to the formation of blood clots in various parts of the body, particularly in unusual sites such as the brain (cerebral venous sinus thrombosis) or abdomen.
Additionally, the immune response can lead to a decrease in the number of platelets in the blood (thrombocytopenia). This combination of clot formation and low platelet levels characterises TTS.
"It's important to note that the clotting syndrome is extremely rare, occurring in a small number of individuals who have received the AstraZeneca vaccine," says Vinod.
Nonetheless, healthcare professionals should closely monitor for this potential side effect, especially in individuals with specific risk factors.
In Malaysia, the Health Ministry has announced that it will seek clarification from AstraZeneca regarding its Covid-19 vaccine, which reportedly causes these rare side effects.
THE PROCESS
THESE are the general processes that Covid-19 vaccines typically underwent before being authorised for public use worldwide during the pandemic:
Preclinical Studies
Before testing in humans, vaccines undergo extensive preclinical studies, which involve laboratory testing and animal studies to evaluate safety and efficacy.
Phase 1 Clinical Trials
These trials involve a small number of participants and primarily assess the safety of the vaccine candidate, as well as its ability to generate an immune response.
Phase 2 Clinical Trials
In this phase, the vaccine is administered to a larger group of volunteers to further evaluate safety, optimal dosage, and immunogenicity.
Phase 3 Clinical Trials
Phase 3 trials involve thousands to tens of thousands of participants and assess both safety and efficacy on a larger scale. Participants are typically randomly assigned to receive either the vaccine or a placebo, and researchers monitor them over time to determine if the vaccine prevents Covid-19 infection or reduces the severity of the disease.
Regulatory Review
After the completion of phase 3 trials, vaccine developers submit data to regulatory agencies, such as the US Food and Drug Administration (FDA) or the European Medicines Agency (EMA), for review. Regulatory agencies independently evaluate the data to ensure that the vaccine meets safety, efficacy, and quality standards.
Emergency Use Authorisation (EUA) or Full Approval
Based on the regulatory review, vaccines may receive emergency use authorisation or full approval for public use.
Emergency use authorisation allows for the use of vaccines during public health emergencies, such as the Covid-19 pandemic, while full approval signifies that the vaccine has met all regulatory requirements for safety, efficacy, and quality.
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