People who are in a panic thinking that they have been in a contact with a novel Coronavirus are rushing for antibody and blood screen test that can identify who had previously been infected and, the hope is, alert who is protected from being exposed to another case of Covi-19.
But as new tests are being conducted, some of the health experts are trying to put in a little of restraint within the excitement that the outcomes of these tests could, for example prevent people to get back to work. Some of the antibody tests have not entirely been validated but they are used for warning. But even those that have been validated, can also give false results. Besides, even an accurate positive test might be hard to interpret as the virus is so new that researchers are still not able to say for sure what sort of results will alert your body immune or how long your immune can hold on the fight.
Researchers are cautioning that policymakers might be making a wrong economic and social decisions by planning to reopen businesses or schools, for example using the limited data that is available, assumptions and what is known so far about other viruses, President Trump a few weeks ago had unveiled a three phased approach towards opening the country. In his speech to the Nation, he stated that some states that have experienced a fall in case counts could start easing social distancing requirements as soon as possible. Some authorities have even went extra miles raising an idea of granting immunity passports to those who have recovered from the virus so as to allow them to continue with their daily life without being restricted.
But scientist and researchers still have doubts with these decisions that are made by the policymakers regarding the economic and social decisions. Angela Rasmussen, who is a Columbia University virologist said that, “before we embark on huge policy decisions, such as issuing immunity certificates to get people back to work, I think it is good that people are saying, ‘Hold up, we don’t know that much about immunity of this virus.”
To be specific, many of the health experts think that an initial infection from the coronavirus called SARS CoV-2, will offer people with immunity to the virus for a limited amount of time. This is the same case that goes to other acute infections from other viruses, which include other coronaviruses.
Anthony Ffauci who is the haed of the National Institute of Allergy and Infectious Diseases while conducting an interview with JAMA said that with such limited data sometimes experts and researchers are forced to act upon historical basis. He added that it was reasonable to assume that the virus is not changing very much. He thinks that if someone is infected now, recovers, and then is exposed once again to the virus, the person is going to be protected.
But the World Health Organization has given out its worries about the presumed immunity as until of now the immunity claim as yet to be proved as scientists are still studying those who have recovered for longer periods. WHO is working on the guidance, which will help in interpreting the results of antibody tests that are also referred to as serologic tests.
Maria Van Kerkhove, from the WHO said that, “Right now we have no evidence that the use of serologic test can show that an individual is immune or is protected from infections.”
There are many questions regarding the antibodies and immunity that scientists are working hard to come up with answers.
But the questions are what are antibody tests? How easily are they accessible? Are they accurate?
The tests normally look for antibodies within the blood, as the antibodies are identical a certain pathogen, and that means their presence is a proof that there was an existence of a certain virus within the person’s body meaning that the person was infected by the coronavirus and mounted an immune response. The hope is that the antibody presence within a person’s body indicate that the person is protected from another infection.
These tests are entirely different from the tests that are used in diagnosing infections, which normally look for pieces of the virus’ genome.
We have seen many commercial antibody tests on the market, but we as of now the Food and Drug Administration has just approved a few via Emergence Use Authorizations. There are health regulations already put in place to warn people regarding the effectiveness of those commercial antibody test kits sold on market.
Stephen Han who is FDA Commissioner said, “I am concerned that some of the antibody tests that are on the market that haven’t gone through FDA scientific review may not be as accurate as we’d like them to be.” He gave this explanation while he met the press earlier this month. He went on to add this, “no test is 100% accurate, but what we don’t want are wildly inaccurate tests.”
Despite the fact that even the best tests might generate false positives (by identifying antibodies that do not really exist) and some might false negatives (missing antibodies that do really exist). Some countries including the U.K. have faced accuracy problems when it comes to the antibody tests, and hence have slowed down their efforts for wide spreading their surveys.
There is a fear when it comes to this case due to imprecise tests and this is because false positive could wrongly lead people to think that they are protected from the virus when they are really not.
Scott Becker, the CEO of the Association of Public Health Laboratories stated that, “Serology testing is not a panacea, when it is used. We need to ensure that there are good quality tests used.”
One problem that is facing the antibody tests for SARS-CoV-2, is that the tests might wrongly pick up antibodies for other types of coronaviruses.
At the globe level, there have only been at least a few thousand people that have been exposed to the other coronaviruses that had previously caused outbreak emergencies, SARS and MERS. But what you have to understand is that, there are four other coronaviruses that circulate in people and account roughly for a quarter of all common odds. It is thought that every person has antibodies to some combination of these coronaviruses, and this means the serological tests for SARS-CoV-2 have to be able to accurately differentiate them.
The next testing method of coronavirus has to identify the full scope of the pandemic and no just look for individual infections.
What information can be obtained from serological results?
The first step is to obtain the antibodies. But when it comes to a step where the obtained antibodies should be interpreted, things get extremely complicated.
Normally, a virus that lead to an acute infection will normally trigger the body’s immune system to start creating specific antibodies. Even when the virus is entirely cleared, the antibodies will remain floating around in the body, ready to attack on the virus in case it returns again and tries to infect again. The virus might infect just a few cells but it can never entirely take control before the immune system banishes it. (Remember this is not the case for viruses that cause chronic infections such as the HVI and many other cases such as the hepatitis C.)
Stephen Goldstein, a University of Utah virologist stated that, “The infection is basically stopped in its tracks before it can go anywhere.” He also added that, “the durability of that protection varies depending on the virus.”
Researchers as well as scientists who have looked at antibodies to other coronaviruses which include common cold that caused foursome and MERS and SARS identified that they lasted for at least a few years, and this indicate that people were protected from being infected at least for that long. From then, protection might start to fade out, and not drop out entirely.
From the experience that was acquired from other viruses that include the other coronaviruses, many researchers and scientists have summarized what the Harvard epidemiologist Marc Lipsitch has referred to as the “educated guess” that appeared in a recent column in the New York Times. This is what make scientists and researchers believe that after someone is infected with SAR-Co-2, his immune system will develop protection against any future infection, the extent of the infection can differ from one person to another as one can be better than the other. That immune body response will protect a person for some medium term, which is at least a year, and then its effectiveness might start to decline.
But a lot of serological tests are no just like pregnancy tests which have just a yes or no result. Serological results identify the levels of antibodies within the person’s blood. This is where things start to get complicated, as scientists cannot say for sure what is the level of antibodies that is need for a person to be entirely protected from being affected with a second Covi-19 case. Besides, they cannot say for how long will someone be safeguarded, even though it is thought that the greater initial tier will take longer to wane as compared to the lower levels.
There is a need of further studies and investigation to understand the duration of protective immunity for the SARS-CoV-2. Currently many of the things that are said are based on assumptions.
Covid-19 spreads extremely fast for normal contact tracing, and therefore there is a need for new digital tools to help. It does not matter whether one has immune, has one of the assumption is that people who have antibodies cannot spread the virus to others. But this has not been proved yet.
Michael Mina, an epidemiologist at Harvard’s T.H. Chan School of Public Health stated that, they don’t have enough immunological or biological data until now to come to a conclusion that if someone with a strong immune response that make them protected from symptoms, cannot be transmitters.
The main challenge as reported by the National Academies pointed out that, there is absolutely no one who knew about the existence of such a virus until just a few months ago. And this means that they have not been able to study what exactly happens to people who have recovered from Coviid-19, and if they have protection against any future infection, how long does this protection last..
One of the key uncertainty that arises from the fact is that the world is in its early stage of the outbreak and the survivors from the initial weeks of the infections in China are, at most three months since they recovered from the infection.
But what else can the antibody tests show?
Besides, identifying those who have been affected the antibody tests can also show at a broader level to what extent the virus has been spreading. These data are so important in determining the extent of the future outbreaks and can help in prior planning of the restrictions communities need to live under. In case there are more people who have been infected than known, a strong likelihood, given number of small infections that might have slipped as well as the testing limitations in countries which include the United States, the a lot of people are assumed of being protected which might be a wrong move.
In the United States, the Centers for Disease Control and Prevention and the National Institutes of Health, all launched serosurveys aiming at assessing the number of people who might have contracted the virus. This goes further to even include employees of major league baseball teams that have also been enlisted within the study hence enrolling thousands of patients.
As of now what have the data from the serosurveys shown us about the antibody generations. Many countries have launched a huge serosurveys in a hope of having a better understanding more on the levels of the antibodies that are being generated by individuals who are recovering from the Covid-19 as well as the general population. As of now, there has been limited data that is released from a couple studies.
Researchers and scientists in Europe have pointed out to strong antibody production in patients within a few weeks after being exposed to infection. On one study they found out that people were generally fast at responding antibodies, which might help to explain the reason behind why many people do not develop severe cases of Covid-19.
But one report that was released this month made things more complicated. Researchers in Shanghai made a report that of 175 patients who were confirmed as being infected with Covid-19, about a third of them had low antibody levels and some had entirely no detectable antibodies. This study suggests that the extent of the antibody response might correlate to the severity of infections, even though that cannot be 100% confirmed as of now. Besides, they also raised concerns that people who have poor antibody response might not be immune from reinfection.
But there are researchers who still argue that conclusions about the immunity cannot just be drawn from what the study has identified. The reason behind their argument is that, there are different kinds of antibodies, and therefore some might exist and the test used wasn’t looking for. Besides, studies in other coronaviruses have proved that antibody responses differ from one person to another, without clear implications for how protected that particular person is from another infection.
And the researchers have also argued that, antibodies cannot be the only way the body uses to protect itself. Immune cells also create memories after any initial infection and can rely on that memory if the same pathogen tries to strike again, even without having antibodies or after the antibody levels have dropped or faded away.
Vineet Menachery stated who is a virologist stated that, People that have lost the serum neutralization does not necessarily mean that they are not going to have some level of immunity, as our body immune system does not forget. It might take a couple of days to generate immune response and be able to fight and clear the virus. He added that if and as soon as protection starts to drop and wane, and people contact the virus once again, it is very likely that they will suffer a more severe illness.
Experts have argued that the confusion over coronavirus case count in China have painted a wrong picture of its spread. There are cases that have been mentioned about the reinfection or reactivated virus. What could this mean?
Health officials in some countries have reported that they have seen some people recovering from the COv-19 only to test positive for the same virus, and this is what is referred to as being reactivation to differentiate it from the second infection.
But some experts are skeptical that either is really occurring, despite the fact that no possibility that can be eliminated as this is the early stage of the outbreak and there are many things that are yet to be known from the research and studies. But there are more likely explanations regarding a positive diagnostic test that comes after a negative test.
One of the likely explanation include the tests that were used to diagnose Covid-19 looks for snippets of the virus genome, its RNA. But the test cannot tell you if what it has identified is evidence of a live virus that can cause infection. As soon as the body has cleared the virus, viral particles tend to remain around for some time. These cannot cause any infections, but can lead to a positive test. This explains to why some people can have a positive test after a negative test. Keep in mind that this does not mean that the virus has been reactivated or became active.
The other likely explanation is that the diagnostic tests normally rely on the patient samples that were pulled from way back in their nasal cavities. The way used to collect the specimen is not foolproof. Testing a sample that was collected improperly might lead to a negative test even if the person has that particular virus. In case the patient gets another test, the test might therefore show that they have the virus.
These two explanation were offered by Jana Broadhurst who is a direct of the Nebraska Biocontainment Unit’s Clinical laboratory.
