Accurate testing is critical to ensuring prompt, effective treatment for patients who experience side effects after receiving the Johnson & Johnson vaccine.
Throughout the COVID-19 pandemic, people around the world looked forward to the advent of a vaccine and a return to normal life. In late 2020, the Food and Drug Administration (FDA) approved the Pfizer and Moderna vaccines for emergency use authorization (EUA), with Janssen (Johnson & Johnson) following in the spring of 2021; meanwhile, Europe approved the AstraZeneca vaccine in late 2020.
What’s the difference between vaccines?
The Pfizer, Moderna, Janssen and AstraZeneca vaccines are all effective in protecting against COVID-19. But there are some differences in their makeup. “The COVID virus is a small piece of RNA,” said Brian Curtis, PhD, senior director of diagnostic hematology at Versiti Diagnostic Labs. “Vaccine makers found a way to take a little piece of that RNA and use it as a vaccine so that when injected into a person, it can be translated and make viral proteins. Once our body sees these viral proteins, it makes antibodies against them.”
But without something to protect it and deliver it to immune cells, RNA is easily degraded in the body. Pfizer and Moderna put their piece of the vaccine RNA into a lipid droplet (a drop of fat) that protects the RNA long enough for white blood cells to recognize it and make antibodies to the COVID-19 virus.
“AstraZeneca and Janssen did things differently; they put a piece of viral DNA into a viral vector,” Dr. Curtis said. Viral vector vaccines use a modified version of a different virus (in this case, an adenovirus, or a common cold virus) to deliver instructions to immune cells. “The adenovirus vector protects the DNA, but it also has a way to interact with cells and deliver the DNA into them,” Dr. Curtis said.
Discovery of COVID vaccine-induced clotting
In April 2021, researchers in Germany and Norway published a paper describing 12 patients who received the AstraZeneca vaccine and experienced a condition called vaccine-induced immune thrombotic thrombocytopenia (VITT) anywhere from 4-30 days afterward. These patients presented with clotting (thrombosis) in unusual places—the brain and abdomen—paradoxically accompanied by low platelet counts (thrombocytopenia). And in April, two months after the Janssen vaccine was approved for use in the U.S., cases of VITT were beginning to be reported to the CDC.
VITT has a high morbidity and mortality rate, requiring prompt diagnosis to aid in the effective treatment of patients. “Accurate assessment of VITT is critical to guiding appropriate drug selection and management of patients with blood clot side effects,” said Ruchika Sharma, MD, associate medical director of Versiti’s platelet immunology laboratory. “Patients receiving incorrect therapies could be at risk for serious bleeding complications or, in some cases, worsening of their existing blood clot(s).”
Testing for VITT
VITT shares similarities with a condition called heparin-induced thrombocytopenia (HIT), in which patients develop antibodies to platelet factor 4 (PF4; a protein that binds to heparin), resulting in a drop in platelet count and paradoxical clotting. The research group in Germany performed HIT testing on sera from VITT patients and found that these patients tested positive, despite never having received heparin. “Initial publications postulated that VITT may have a similar mechanism to HIT, in which patients have an inflammatory response to the vaccine and may develop antibodies to PF4,” Dr. Sharma said.
Versiti Diagnostic Labs’ expertise in platelet testing
Because of Versiti Diagnostic Labs’ established expertise in HIT testing, physicians and researchers began to lean on Versiti to better understand how they could screen patients for VITT. “Versiti's Platelet and Neutrophil Immunology Lab is a national expert in advancing platelet immunology testing,” Dr. Sharma said. “We started receiving requests from clinicians across the country who were beginning to see patients presenting with VITT. They were looking for information about the right tests for these patients, how to best diagnose them, and how to put diagnostic information together.
“We thought it would be the right time to develop a comprehensive VITT diagnostic offering that not only informs clinicians of the correct tests to order for these patients, but also helps ensure patients with suspected VITT are sent through a specific testing requisition so that we can track them and order the right tests for them,” she said. “The platelet immunology lab has a reputation for being a national expert in immune-mediated platelet disorders, so we were the natural leaders to develop this initial diagnostic panel for a new, emerging and rare—but serious—complication of vaccines. Ours is the first panel in the United States that has this comprehensive offering for VITT.”
“The hope and the expectation are that VITT continues to be exceedingly rare,” she continued. “Our goal is not to highlight this as a complication, but to raise awareness about VITT to clinicians and provide them with an accurate diagnostic offering to aid in prompt and accurate patient management.”
About the experts:
Brian Curtis, PhD, D(ABMLI), MT(ASCP)SBB, is the senior director of diagnostic hematology at Versiti Diagnostic Labs and senior investigator at Versiti Blood Research Institute.
Ruchika Sharma, MD, is the associate medical director of hematology at Versiti Diagnostic Labs and an assistant professor of pediatrics – hematology/oncology at the Medical College of Wisconsin.