Covid-19 patients that have recovered might still have to be careful and follow social distance and self isolation rules. When your immune system encounters a new pathogen and successfully defends the host; the immune system will release antibodies specific to that pathogen. If the host comes into contact with that pathogen again these antibodies will recognise the pathogen and mount a far quicker defence and the host may not even be aware, they have come in contact with the pathogen or may present with less severe symptoms.
The whole premise of vaccine is based on the immune system creating specific antibodies to a pathogen. In 1796 Edward Jenner deliberately infected a 10-year-old child called James Phipps with the Vaccinia virus otherwise known as cowpox. Vaccinia belongs to the same genus as the Variola virus also known as Smallpox. This deadly disease is thought to of killed 300-500 million people. Jenner repeated the experiment on 10 other people over 2 years. His work shown that infection with the cowpox virus leads to resistance to the smallpox virus and this eventually led to vaccinations. Interestingly ‘vacca’ in Latin is cow.
Covid-19 is a virus caused by a new coronavirus and patients that have recovered from this infection will have specific antibodies made from the immune system. Is this enough to offer protection against reinfection?
There has been news of recovered Covid-19 patients being infected again. Currently there is little research on Covid-19 even less research on immunity to this virus. Assumptions for immunity to Covid-19 for now have to be made from previous coronavirus epidemics such as the SARS outbreak in 2002-2003.
In cases where patients have been infected again with Covid-19 it must be established if this is reinfection the main points are.
- Patients that tested positive for Covid-19 and then tested negative could have a false negative test result. Patients in this case may have had the infection for a longer period of time and then tested negative but the test may be a false negative. Every test has false negative and false positives.
- Patients that tested positive after being given the all clear may have had weaker immune systems. Therefore, the immune system cannot mount the same defence when they come in contact with the same virus as someone with a stronger immune system.
- A study done after the 2002-2003 SARS outbreak in China shown that specific antibodies to SARS remained in the blood for 2 years and started to reduce in year 3 post infection (Wu et al., 2007).
- There are two strains of Covid-19 L-type and S-type the L-type is more aggressive. This should be taken into account when testing.
The reported cases of reinfection may be due to a false negative result and reinfection may be due to a weak immune system. Recovered Covid-19 patients will most likely have immunity but for how long? Until more research for immunity to Covid-19 is conducted it is suggested that recovered patients follow the same social distancing and self-isolation as everybody else. Aggressive testing for patients infected with Covid-19 that appear to have recovered would seem prudent.
Fortunately, Covid-19 appears to have a slower mutation rate than that of influenzas which bodes well for vaccine design and new strains appearing in the near future.
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- WU, L.-P., WANG, N.-C., CHANG, Y.-H., TIAN, X.-Y., NA, D.-Y., ZHANG, L.-Y., ZHENG, L., LAN, T., WANG, L.-F. & LIANG, G.-D. 2007. Duration of antibody responses after severe acute respiratory syndrome. Emerging infectious diseases, 13, 1562-1564.