'I Got Corona Again:' What this Means for Reinfection & Immunity
'I Got Corona, Again,' read the Instagram post by a US-based graphic designer. In the post he details how he first tested positive for COVID-19 in March, when from his return from New York, he showed mild symptoms of the disease. What started as a mild cough and low grade fever developed into a cough severe enough to get approval for a test. After a COVID positive result, he was in home quarantine and eventually recovered.
Then in the first week of July, he once again came down with a terrible throat pain followed by fever that refused to go away. He was taken to a hospital where he tested positive for Coronavirus. Three months after his first infection.
An article in Vox, on 12 July, by a doctor in the US talks about how his patient tested positive for coronavirus again, 3 months after first contracting it. And this time around, the infection was much worse. "High fever, shortness of breath, and hypoxia, resulting in multiple trips to the hospital."
He dismissed the possibility of his patient suffering from a long tail COVID that lasts for upto 3 months in some patients - his patient had tested negative twice in March via RT-PCR and remained healthy in between.
Coronavirus Immunity May Disappear Within Months: Study
On 12 July, in a report in The Guardian, they quoted a King's College London study that found a steep drop in antibody levels in patients three months after recovering from COVID-19.
This is a first longitudinal study, meaning, it tracks patients over a period of time. Scientists looked at the immune response in 90 patients and healthcare workers and found that antibodies that kick in to fight the virus peaked three weeks after symptoms and then started to quickly decline.
In 60% patients there was significant antibody response at the peak of their infection and only 17% still had that level of antibodies three months later. In some cases there was no antibody response that could be detected.
The antibodies fell in a short period of time nearly 23-fold.
In a significant observation, the study found that those with a more severe form of the disease, produced more antibodies that lasted longer compared to those with mild symptoms.
If this holds true, patients could get reinfected during an eventual second wave.
How Long Does Immunity Last in Other Coronaviruses?
In an earlier story on FIT, where we examined the logic of 'immunity passports', this is what we wrote:
A study of over 170 people who had been infected by Severe Acute Respiratory Syndrome (caused by another strain of coronavirus, called SARS-CoV) found that SARS-specific antibodies were maintained for an average of two years in their bodies. This meant that SARS patients might be susceptible to reinfection three years after initial exposure. Similar findings were also arrived at for MERS, but since the number of patients affected was limited, the data obtained may be considered inadequate.
As for the seasonal coronaviruses that cause common colds, immunity seems to last for a shorter period of time, even if there are more number of antibodies, which is why getting a common cold is more frequent.
The Guardian quoted Prof Stuart Neil, a co-author on the study, as saying "It looks like Sars-Cov-2, the virus that causes COVID-19, might be falling into that pattern as well.”
What Does All of this Mean for Herd Immunity, Vaccine Development?
Over 150 vaccine candidates are in various stages of development with several in human trial phases. But for a while now, experts have warned that perhaps no vaccine will work against the coronavirus. Or at best, vaccines will provide limited protection, needing regular booster doses.
The Oxford vaccine, that had raced ahead in the vaccine game, has shown limited results in the animal trial data that was eventually released. While the vaccine appeared to protect the animals from serious infection, they still became infected and may have been able to pass on the virus.
Study authors warn that if the COVID-19 infection is giving a limited antibody response, a vaccine would do the same.
This also raises questions about herd immunity as a defence mechanism against COVID-19.
In an earlier interview with FIT Dr Sumit Ray, a critical care specialist in Delhi NCR, had explained, “Once more and more people are exposed to an infection, mostly a viral infection, they either build immunity for it or they succumb to the disease.”
“If a larger number of people build up immunity, the transmission rate goes down and there’s a drop in the level of cases and deaths, bringing down the overall severity of the disease. This breaks the cycle of transmission.”Dr Sumit Ray
This is because when people build immunity against a virus, they not only are protecting themselves against it, but also are preventing themselves from becoming carriers of the disease and transmit it to someone else.
The best way to achieve this is by vaccination.
A number of countries, including Sweden, floated the idea of somehow letting their population get exposed to coronavirus in the hope of ultimately achieving herd immunity. But as number of cases and deaths have skyrocketed, that plan has come under heavy criticism.
But if immunity itself is short-lived, herd immunity as a defence doesn't work.
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