Your questions about testing for coronavirus and antibodies

Can I Be Immune to Covid-19?

Aside from durability, not all vaccines have complete protection, for example, the annual flu shot ranges in effectiveness and works better for children than for the rest of the population. In 2019, it was less than 50% effective in preventing the flu, but there were still major benefits.

While our hopes for a return to a ’ normal world" lie in a vaccine primarily and progress is being made in that regard with over 150 vaccines being investigated worldwide - we still have major questions that remain unanswered.

What is immunity?

When the general public uses the term immunity - it is thought of as an almost absolute protection. However in many cases immunity is anything but absolute. The flu vaccine, for example reduces the risk of more severe disease for example rather than infer absolute immunity.

How does immunity work?

In the case of COVID-19 the main mechanism is through the production of antibodies. But it should be noted that one study has found that as many as 8.5% of those infected had zero detectable antibodies. Additionally it is thought as survivors tend to be younger - there are also cell-mediated arms of the immune system that can neutralize the virus through white blood cells and cytokines.

As Charles Cairns, the dean of Drexel University College of Medicine has said: “those who have inflammation mount an immune response that’s more detectable and potentially more robust.” This further points to the potential importance of cell-mediated immune response in the case coronavirus.

How long does immunity last?

We do not know yet. However we do know of cases of patients who had a recurrent infection with COVID-19 and we also know that some other coronavirus infections confer only temporary immunity, in some cases as few as a few months. More data is required.

What factors affect immunity?

Essentially the level and duration of immunity from an infectious disease are highly correlated with the severity and duration of the immune response to the infection. As such infections with more severe symptoms tend to a stronger immune response thus inferring a higher level and duration of immunity. Conversely, mild or asymptomatic cases lead to generally lower antibody levels and thus potentially lower levels of, and duration of immunity. However we do not yet know if that is in fact valid for COVID-19.

What does immunity data imply re a potential vaccine?

Simply said - there is insufficient data to answer this with any degree of certainty.

"Obviously, a vaccine that works 100% of the time would be ideal, but that is not realistic," said Dr. John Mascola, director of the National Institutes of Health Vaccine Research Center.

The level of response to a vaccine may vary from a slight reduction in severity of the disease in some populations or people, to a very high level of protection in most individuals. With so many vaccines in development it is likely that the results will also vary.

Until we have the results of phase III trials which will measure the actual efficacy of the vaccine we won’t know for sure for any individual vaccine. We will thereafter have a better understanding of the relationship and degree thereof between antibody levels and immunity.

It should be noted however than in the case of the influenza vaccine which can have an effectiveness of only 50% in preventing the flu - still confers major benefits not only to those protected but the community as a whole by decreasing the number of infections, and deaths while also decreasing the number of those who become severely ill and require hospitalization, intubation and admission to intensive care.

How do the different vaccines being investigated work?

Different approaches are being used by various institutions to create a COVID-19 vaccine. The group from Oxford and its partner AstraZeneca for example are using the more traditional approach of an attenuated virus which is a virus that doesn’t make people sick but infers immunity. Yet others with Moderna and Pfizer being well known examples are using proteins that can "trick the immune system into mounting an effective response against future infection.”

Once there is a vaccine - who should get it?

Again we don’t know yet until results from the trials come in at the very least. However if as may be the case - previous infection with COVID-19 does not infer as strong or as long a level of immunity - then most people would likely be recommended to be vaccinated.

Additionally like in the case of the flu vaccine, a coronavirus vaccine might also work better for certain sub-groups.

What if the COVID-19 virus mutates?

The structure and biology of this virus is such that it is covered in tiny spikes called surface proteins. Most experts indicate that most vaccines being developed currently are likely to work into the future as sufficient mutation to incur lack of efficacy is unlikely - though a finite possibility does exist.

I was pretty sick a few months ago, and it wasn't the flu. Should I get an antibody test?

An antibody test detects the level of antibodies against Covid 19 in your blood. The antibody test is limited in that we don't know how long the antibodies last in a person's body. It also won't show the antibodies if you currently have the infection, even if you don't have any symptoms.

If you get a positive antibody test result it shows you likely had Covid 19. This doesn't necessarily mean you’re immune from getting reinfected, we simply don't know how long the antibodies last, or how much immunity they provide. Depending on the type of experience you had and your test results, you may be retested, and perhaps asked to take part in a blood plasma donation, to help others in developing treatments for the disease.

If you get a negative antibody test result it means you likely did not have the virus in the past, although it could just be too soon. The antibodies can take typically between 1 to 3 weeks to appear. A negative test also doesn't mean you don't have it now. The antibody test does not test for current infections, only past ones. Even if you don't have any symptoms, it could mean you were recently exposed and still able to transmit the virus to others.

If I get a test and I test negative that means I'm fine, right?

No, not necessarily. The Covid 19, like any other test, only tests for the current state, and means only active infections. You may have been exposed but not infected yet, which would result in a negative test, even though you could pass the infection to others. The CDC suggests that testing is best used to confirm suspected cases to help with exposure tracing and managing the disease in those who have more severe illness.


Is there a test to see if I had the virus before?

Yes, there is a blood test that can show if a person has had Covid 19 in the past. Over time, this could help experts understand how many people were infected without knowing it. Experts are also using blood tests to study whether a person who has had Covid 19 could get it again.


Should I get tested for Covid 19?

Testing for Covid 19 tells us if someone has a current infection. It doesn't tell us if a person has been recently exposed or has had the virus in the past. According to the CDC, not everyone needs to be tested, and there are criteria that doctors, states, and local officials use to determine if a test is needed. Decisions are made based on symptoms and criteria, that may be related to cost or limited tests or testing materials.

Since many people only get a mild illness and recover at home, they may not need to be tested. Testing helps identify and diagnose more complex cases, to rule out other diseases and conditions. If you believe you should have a test, contact your doctor to discuss the risk factors, symptoms, and concerns.

Is there a test for the virus that causes Covid 19?

Yes, there are tests to see if you have Covid 19. If your doctor or nurse suspects you have it , they might take a swab from inside your nose and have it tested. If you’re coughing up mucus, they might also test that sample. These tests can help your doctor figure out if you have Covid 19 or another illness.

In some areas, it might not be possible to test everyone who might have been exposed to the virus. If your doctor can’t test you, they might tell you to stay home, avoid other people, and call if your symptoms get worse.

Will my child need tests?

If a doctor or nurse suspects your child has Covid 19, they might take a swab from inside their nose for testing. These tests can help the doctor figure out if your child has Covid 19 or another illness.

In some areas, it might not be possible to test everyone who might have been exposed to the virus. If the doctor can’t test your child, they might tell you to keep them home and away from other people, and call if symptoms get worse.