A study from Spain suggests that 44% of people with mild or asymptomatic infection have very low antibody levels with little neutralizing capacity.
This means that a positive antibody test may not guarantee protection against the Coronavirus (known officially as SARS-CoV-2).
The tests, performed with plasma from people who have been exposed to the Coronavirus and have generated neutralizing antibodies against the virus, shows that 44% of people who have been mildly or asymptomatically infected have a very low level of neutralizing antibodies.
And half of these have no neutralizing activity.
This indicates that people who have been infected may not be protected against another infection.
The study shows that this trend is reversed in people who have had severe disease, who have up to 10 times more antibodies than individuals with mild infection.
The research states that: “In the case of people who had been hospitalised, they generated approximately 10 times more neutralising antibodies than those who had a mild clinical course.“
As a result of this, scientists warn that the presence of antibodies by itself may not guarantee immunity to a second infection, and insist on the need for everyone to maintain basic precautions: hand hygiene, mask use and social distancing.
The research was made by IrsiCaixa AIDS Research Institute. The data is from a set of 111 plasma samples from people who have generated antibodies against the SARS-CoV-2 Coronavirus and who experienced varying degrees of severity of the virus.
In the similar SARS virus, research shows that there is an antibody decline over time.
This means that after a couple of years, the number of antibodies has declined significantly.
We also see from other coronaviruses, from ones that cause coughs and colds, that people seem to not have particularly long-term immunity, allowing them to get re-infected later.
This is very bad news for people who are hoping for herd-immunity, as if many people don’t get immune against the virus, herd-immunity will not be possible to achieve.