COVID-19 vaccines

Experts do not recommend antibody testing after COVID-19 vaccination

Sofia Tomacruz
Experts do not recommend antibody testing after COVID-19 vaccination

PROTECTION. The Bacoor City government has opened its eighth vaccination hub at the SM Mall. The site was allotted 600 doses of Sinovac vaccine for pre-registered residents on its opening day on June 1.

Dennis Abrina/Rappler

Experts studying vaccines in the Philippines say such tests are only one measurement of immune response to a virus and does not answer whether one is protected against COVID-19 after vaccination

Experts studying coronavirus vaccines in the Philippines said on Wednesday, June 2, that they did not recommend vaccinated individuals to undergo antibody testing to determine whether or not vaccines have given them protection against COVID-19. 

In a House of Representatives health committee hearing on Wednesday, scientists and medical experts leading the Department of Science and Technology’s (DOST) studies on vaccines, warned that individual testing for antibodies after getting vaccinated may sow confusion as there was still no single test available that could determine the level of protection one had against the virus. 

Quezon 4th District Representative Angelina “Helen” Tan asked experts to explain whether results from a neutralizing antibody test could be used as basis for the status of one’s immune system after getting vaccinated. Tan asked the question after disclosing she and her husband had themselves tested after getting vaccinated, with her husband showing “favorable” results and her receiving “negative” results. 

DOST Philippine Council Health Research and Development (PCHRD) Executive Director Jaime Montoya said that neutralizing antibody tests only measure one type of immune response to the vaccine. 

“It only describes what we call the antibody-based immunity. There is also what we call the cell-based immunity, which is not actually covered by these tests and are covered by other tests which are more complicated and sophisticated,” he said. 

Montoya added that while the presence of antibodies “means that definitely you have some protection already,” it does not wholly determine whether you have protection against a virus after getting vaccinated. 

“To say that you are actually protected already, that is another question because it only tells you that there are antibodies but we are not sure whether those antibodies actually neutralize the SARS-Cov-2,” he said. 

Infectious disease specialist Dr Regina Berba of the University of the Philippines, Manila-National Institutes of Health (NIH) also said experts did not recommend that individuals test themselves for antibodies after getting vaccinated. 

“We should not on an individual basis recommend to do antibody testing. Perhaps (it should) only (be) in the setting of trials right now so we see trends and mean averages of what exactly these numbers mean,” Berba said. 

“The WHO (World Health Organization), the CDC (US Centers for Disease Control), global experts really don’t recommend that individually we do antibody testing because it is a very complex response to the vaccines,” she added. 

Should ‘negative’ results make you worry?

During the hearing, several lawmakers had reported that as more vaccinated individuals were testing their antibody levels after getting vaccinated, varying results sowed confusion on whether or not vaccines received were effective against COVID-19.

Batanese Representative Ciriaco “Jun” Gato asked experts to clarify this and explain whether one should be worried about results showing “zero” levels of neutralizing antibodies. 

Berba said such results do not mean the vaccine they received was ineffective. “It does not 100% correlate with protection…. Our countrymen who eventually have a negative test should not have a decline in their confidence in the vaccine,” she said. 

Dr Michelle De Vera of the Philippine Society for Allergy, Asthma, and Immunology likewise explained that antibody testing is only one way to measure one’s response to a vaccine or virus. 

“The immune system is amazingly sophisticated so one measurement cannot totally measure the entire immune response of your system to the COVID virus….  In the end, the proof is in the pudding and so as Dr Berba said, we’re also going to follow people over time to see if they actually contract the disease or not because that will be the real test for whether you’re protected against this virus or not,” De Vera said. 

In an official statement, the Department of Health echoed experts, saying it did not recommend antibody testing to confirm protection against COVID-19 after vaccination. 

“A negative antibody test does not mean that the COVID-19 vaccine did not work. We advise the public to consult their doctor before doing any diagnostic test because these should only be performed with professional guidance,” it said. 

The United States Food and Drug Administration, as well as its Centers for Disease Control had both earlier advised against testing one’s antibody levels to determine whether they were protected after getting vaccinated. 

“Antibody testing is not currently recommended to assess for immunity to COVID-19 following COVID-19 vaccination or to assess the need for vaccination in an unvaccinated person…. Post-vaccination serologic test results will be negative in persons without history of previous natural infection if the test used does not detect antibodies induced by the vaccine,” the CDC said. 

The US FDA had likewise warned that misinterpreting antibody test results could potentially lead people to take fewer precautions against COVID-19 and that more research needed to be done on testing after vaccination.

Like in the Philippines, Montoya said currently available antibody tests were validated and given emergency use authorization to test whether one had a previous infection. “It is not stated there that if you use it, it will tell you if you are protected or not, if you are immune or not,” he said. – Rappler.com

Sofia Tomacruz

Sofia Tomacruz covers foreign affairs and is the lead reporter on the coronavirus pandemic. She also writes stories on the treatment of women and children. Follow her on Twitter via @sofiatomacruz. Email her at sofia.tomacruz@rappler.com.