Important decisions about this question are being made, as they must be, based on only glimmers of data.
Among the many uncertainties that remain about Covid-19 is how the human immune system responds to infection and what that means for the spread of the disease. Immunity after any infection can range from lifelong and complete to nearly nonexistent. So far, however, only the first glimmers of data are available about immunity to SARS-CoV-2, the coronavirus that causes Covid-19.
What can scientists, and the decision-makers who rely on science to inform policies, do in such a situation? The best approach is to construct a conceptual model — a set of assumptions about how immunity might work — based on current knowledge of the immune system and information about related viruses, and then identify how each aspect of that model might be wrong, how one would know and what the implications would be. Next, scientists should set out to work to improve this understanding with observation and experiment.
The ideal scenario — once infected, a person is completely immune for life — is correct for a number of infections. The Danish physician Peter Panum famously figured this out for measles when he visited the Faroe Islands (between Scotland and Iceland) during an outbreak in 1846 and found that residents over 65 who had been alive during a previous outbreak in 1781 were protected. This striking observation helped launch the fields of immunology and epidemiology — and ever since, as in many other disciplines, the scientific community has learned that often things are more complicated.
One example of “more complicated” is immunity to coronaviruses, a large group of viruses that sometimes jump from animal hosts to humans: SARS-CoV-2 is the third major coronavirus epidemic to affect humans in recent times, after the SARS outbreak of 2002-3 and the MERS outbreak that started in 2012.
In Other News – Coronavirus cases hit 216 as 8 more test positive
The number of Coronavirus cases has hit 216 as eight more cases test positive for the disease.
Health CAS Dr Mercy Mwangangi said five of the new patients are Kenyans while three are foreign nationals.
Out of the eight cases, six have a history of travel from UAE, UK, Pakistan, Zambia and Comoros. We have six cases from Nairobi county, Siaya and Nakuru one each. read more
Source – Nytimes