Introduction to COVID-19 Vaccines:
Immunization is an essential component of primary health care and a basic human right. It is also one of the best health investments people can make with their money. Vaccines are also important in preventing and controlling infectious disease outbreaks. They support global health security and will be critical in the fight against antimicrobial resistance.
A vaccine must go through three clinical trials. Pre-clinical trials are conducted on laboratory animals. The first phase examines the vaccine's safety as well as an individual's immune response. Phase two trials also assess an individual's safety and ability to produce an immune response. The third phase of the clinical trial includes a large number of participants to determine the efficacy of the vaccine against the specific disease.
There are currently 38 approved vaccines (approved by various national government bodies) and ten vaccines on the WHO (World Health Organization) Emergency Use List (EUL). A regulatory mechanism for the use of medicines and vaccines is referred to as emergency use authorization. This mechanism aids in reducing or preventing the negative effects of COVID-19 symptoms. This emergency authorization evaluates several critical aspects such as safety and security. WHO has granted the following vaccines emergency use listing:
-
Sputnik V (Gamaleya).
-
CoronaVac (Sinovac).
-
Covilo (Sinopharm).
-
Spikevax (Moderna).
-
Ad26.COV2.S (Johnson & Johnson).
-
Covaxin (Bharat Biotech).
-
Comirnaty (Pfizer and BioNTechv).
-
Nuvaxovid (Novovax).
-
Covovax and Covishield (Serum Institute of India).
-
Vaxzevria (Oxford/AstraZeneca).
COVID-19 Vaccines: How Do They Work?
The entry of virus into the human body is followed by its invasion and multiplication within the cells. With the help of white blood cells, the body's immune system prevents this infection from spreading. The virus and damaged cells are engulfed and digested by macrophages (a type of white blood cell). These macrophages leave behind antigens, which are virus parts. B-lymphocytes, which are defensive white blood cells, produce antibodies that attempt to destroy antigens left behind by macrophages. Another type of white blood cell, T-lymphocytes, attacks infected cells in the body.
These processes can take days to weeks, and the immune system eventually defeats the infection. If the pathogen re-invades the body after the initial infection, the immune system recalls how to fight it. Some T-lymphocytes remain in the body and will attack again if the body comes into contact with the same virus.
COVID-19 vaccines are intended to provide the same immunity as infection with the virus. Different vaccines work in different ways, but all vaccines result in forming of B and T lymphocytes. The lymphocytes remember how to fight the virus in the event that the person becomes infected again in the future. Seven days after being fully vaccinated, the case division between vaccinated individuals and those who took the placebo indicates a vaccine efficacy rate of more than 90 %.
Timeline of the Johnson & Johnson Vaccine:
The FDA authorized the emergency use for Johnson & Johnson COVID-19 vaccine on February 27, 2021, and the Advisory committee on immunization practices (ACIP) interim recommendation for its use was published on March 2, 2021. On April 13, 2021, the FDA issued a pause on the use of the Johnson & Johnson vaccine in view of the thrombolytic side effects, which were then reviewed, and the use of the vaccination resumed after ten days. On October 20, 2021, FDA authorized the administration of booster doses of Pfizer-BioNTech, Moderna, and Johnson & Johnson vaccines in eligible individuals above the age of 18 years. The FDA revised the Fact Sheets for Healthcare Providers and Recipients on Janssen (Johnson and Johnson) vaccine on December 14, 2021. Those with a history of thrombosis with thrombocytopenia (TTS) after receiving the Janssen COVID-19 vaccine or any other adenovirus-vectored COVID-19 vaccine are contraindicated, and the risks of TTS following vaccination have been updated. FDA has limited the use of the Janssen (J&J) vaccine to certain individuals starting May 5, 2022, and a fact sheet for healthcare providers, recipients, and caregivers has been updated to include the risks of blood clots with low levels of blood platelets.
What Is the Reason for the Pause on Johnson and Johnson Vaccine?
The Johnson & Johnson COVID-19 single-dose vaccine received Emergency Use Authorization (EUA) from the United States Food and Drug Administration for its single-dose COVID-19 vaccine, developed by Johnson & Johnson’s Janssen Pharmaceutical Companies, to prevent COVID-19 in individuals 18 years of age and older. Following an updated analysis, evaluation, and investigation of reported cases, the FDA deduced that the risk of thrombosis with thrombocytopenia syndrome (TTS), a syndrome of rare and potentially life-threatening blood clots in addition to low levels of blood platelets, with symptoms onset one to two weeks after administration of the Johnson & Johnson COVID-19 vaccine, warrants limiting the vaccine’s authorized use.
Individuals 18 years or older for whom other authorized or approved COVID-19 vaccines are not available or clinically appropriate, and for individuals, 18 years of age and older who choose to receive the Janssen COVID-19 vaccine because they would not otherwise receive a COVID-19 vaccine; the effective benefits of vaccines in COVID-19 prevention outweigh its known and potential risks.
The fact sheet available for healthcare providers administering vaccines presently reflects the revision of the Janssen COVID-19 Vaccine’s authorized use and includes a warning statement at the beginning of the fact sheet that summarizes information on the risk for TTS. The fact sheet for recipients and caregivers has also been updated with information on the revision to the vaccine’s authorized use, as well as updated information on the risk of blood clots with low levels of blood platelets.
Conclusion:
To monitor the safety of COVID-19 vaccines that are approved and authorized for emergency use, the FDA has a robust safety surveillance system. In collaboration with the Centers for Disease Control and Prevention (CDC), the Centers for Medicare and Medicaid Services, the Department of Veterans Affairs, and other academic and large non-government healthcare data systems, the FDA is monitoring COVID-19 vaccine safety through both passive and active safety surveillance systems. Therefore, it is of utmost importance to stay updated with the changes and to continue to get vaccinated.
