THERE is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.
This was echoed in a statement by the World Health Organization (WHO) last week: “As of 24 April 2020, no study has evaluated whether the presence of antibodies to SARS-CoV-2 (Covid-19) confers immunity to subsequent infection by this virus in humans.”
Studies out of Beijing indicate those who have been infected with Covid-19 develop a protective antibody – but it isn’t clear how long the protection lasts.
Normally, when we are infected with a new microbe to which we are not immune, like Covid-19, our immune system launches an attack via the production of antibodies against the microbe. This process takes place after some days of being infected, as we move from being asymptomatic to being symptomatic. Once we are able to fight off the microbe by the production of antibodies against it, we are usually conferred long-term immunity as our immune system continues to produce these antibodies for life. This is what we call primary immunity.
On the other hand, vaccination, which is the inoculation with either particles of the microbe or a weakened form of the microbe, mimics an infection without deleterious symptoms while our immune system launces an attack against these and develops immunity to the microbe being vaccinated against. Because the immune response is not triggered by the actual microbe, this is termed secondary immunity, but the end result is still be the same. We produce in the long-term an antibody against the microbe and so we are immune. This is how vaccines against Measles, Mumps, Rubella, Yellow Fever, Polio etc. work.
However, respiratory viruses like influenza and coronaviruses tend to mutate and change their surface proteins often by a process called antigenic drift. This renders the long-term antibodies against them ineffective and we have to undergo the process of achieving primary immunity once again, if we are infected with the new strain of the virus. That is why we have to get annual flu shots as a new strain of the virus, against which we are not immune, emerges every year and the vaccine is changed as scientists keep tabs on the antigenic drift. That would mean if we should catch this strain and we are not inoculated against it, we get can respiratory symptoms and run the risk of complications and even death.
With the Novel Coronavirus (Covid-19), we have not yet developed a vaccine. If we are unfortunate to be infected with Covid-19, primary immunity will take place. However, as we develop symptoms, there is a likelihood of the complications and death, especially among the vulnerable. Because debilitation and death are real possibilities, before we develop a vaccine, social distancing to prevent being infected is our best bet as recommended by international health bodies, like the WHO, based on evidence.
However, based on the available data, it seems likely that having the disease once, results in immunity in most individuals – as is seen with other coronaviruses. Coronaviruses are not new, they’ve been around for a long, long time and many species – not just humans – get them. So, we know a fair amount about coronaviruses in general. For the most part, the feeling is once you have had a specific coronavirus, you are immune. We do not have enough data to say that with this coronavirus, but it is likely. This means that people who initially recovered are more likely to relapse rather than get reinfected with the virus.
The fact remains however that, the immune response to Covid-19 is not yet understood fully and ongoing studies results in changes in our prevention and management of the disease. In 2012, patients with Middle Eastern Respiratory Syndrome (MERS-Cov) infection were unlikely to be reinfected shortly after they recovered, but it is not yet known whether similar immune protection will be observed for patients with Covid-19.
While further studies are needed to understand whether it is possible for an individual to be reinfected with new coronavirus, experts recommend those who have been infected follow the hygiene steps outlined by Centres for Disease Control and Prevention (CDC) and WHO which include staying away from people who are sick, frequently washing hands, and covering coughs and sneezes.
Dr Visham Bhimull MBBS (UWI), Diploma in Family Medicine (UWI)