- Immunity to the novel coronavirus virus has been the subject of several studies. It’s not important just for managing patients and public health measures, but also for the development of vaccines and vaccination guidelines.
- A brand new study shows that coronavirus immunity can last anywhere between five to seven months, with researchers speculating that it can even last up to two years.
- The scientists set out to develop an accurate antibody test, and the research also allowed them to measure COVID-19 immunity in nearly 6,000 survivors.
Observing the health measures authorities recommend to prevent the spread of the novel coronavirus won’t just help you avoid a COVID-19 infection. Reducing the transmission rate also helps hospitals attend to patients without worrying about local healthcare systems becoming overloaded. Wearing masks, social distancing, and washing hands often also buy much needed time for researchers to finalize vaccine trials, create new treatment protocols, and deliver the kind of coronavirus data that takes time to collect.
Studying COVID-19 immunity is the kind of research that needs time. The first studies that appeared early in the pandemic indicated that monkeys who survived the illness would indeed develop immunity. But the early conclusions could not predict how long immunity would last or how mutations to the virus might affect immunity. Studies on humans that arrived much later indicated that coronavirus immunity might not last very long at all. Some scientists observed that the antibodies that neutralize the SARS-CoV-2 virus could disappear within a few months following recovery. Others countered that it’s not just antibodies that prove immunity — T cells that can remember and kill the pathogen are equally important.
Now, nearly 10 months after the virus first began sweeping across the world, we have a study that says COVID-19 immunity lasts much longer than we thought.
Immunity isn’t important just for patients, the doctors treating them, and the public officials who develop new health protocols. It’s also important for vaccine makers. The longer-lasting the protection is, the better the vaccines will work. Even if they’re not 100% effective and even if more and more people are worried about COVID-19 vaccine safety, a vaccine that induces long-term protection can significantly reduce the spread of the disease.
We’ve seen recent reports detailing cases of coronavirus reinfection. Genetic analyses of the two SARS-CoV-2 strains that infected the same individuals a few months apart proved the existence of such cases. But so far, only a few of them have been confirmed, including at least one of them in the US. This seems to be the first indication that most of the more than 40 million people who tested positive for COVID-19 are still protected. Not to mention that the real figure of COVID-19 survivors might be significantly higher. Many people got the virus and never developed symptoms, so they were never tested. Others may not have had access to testing in the first place.
This brings us to the latest research paper on immunity from the University of Arizona College of Medicine in Tucson. Dr. Deepta Bhattacharya and his colleagues published their paper in Immunity magazine, via MedicalNewsToday. They were able to prove that COVID-19 immunity generally lasts between five and seven months, which is much better than expected. Some of those confirmed reinfections occurred after just two to three months.
The scientists set out to develop a COVID-19 antibody test with a high rate of accuracy. Antibody testing has been controversial because many of the tests that have been used turned out to be unreliable. False-positive or false-negative results can be misleading and dangerous. One large health authority even said that antibody testing might be useless until tests become more reliable.
Bhattacharya and his team started recruiting volunteers on April 20th to develop an accurate test. They developed an assay that has to provide two positive results for different components of the virus’s spike protein. The test looks for the receptor-binding domain of the spike protein (RBD) and then the S2 section of the same protein. The test is considered positive only if it finds antibodies for both of those sections.
The researchers used plasma with live virus to test the samples from volunteers. Out of 5,882 samples, only one test was a false positive. These conclusions allowed the researchers to seek and obtain an emergency use authorization for their test from the FDA. But the direct side-effect of the search for a more reliable antibody test concerns immunity. The scientists also looked at how long the immunity lasted for people who tested positive in the early months of the pandemic.
“We clearly see high-quality antibodies still being produced 5–7 months after SARS-CoV-2 infection,” says Dr. Deepta Bhattacharya. “Many concerns have been expressed about immunity against COVID-19 not lasting. We used this study to investigate that question and found immunity is stable for at least 5 months.”
The researcher also made the same point that we’ve heard from other scientists studying COVID-19 immunity. SARS immunity lasted anywhere between 12 to 17 months, and there were hopes that SARS-CoV-2 immunity might be similar. “If SARS-CoV-2 is anything like the first one, we expect antibodies to last at least 2 years, and it would be unlikely for anything much shorter,” the researcher said.
The authors have also explained the recent studies that said neutralizing antibodies can disappear a few weeks after infection. They said that in a typical viral infection, the first wave of antibody-producing immune cells has a short life. After that, a smaller number of cells that can produce antibodies arrive, and they can last for years.
The team did acknowledge two limitations of the study. Some of the individuals tested for antibodies may have lost their immunity before joining the research. They would have tested negative. Also, there’s no telling what happens after 226 days. That’s the maximum follow-up for the study. As with other COVID-19 studies, more research is definitely needed for coronavirus immunity. We’ll obviously need to wait even longer to see whether immunity extends beyond seven months.
The finalized research from vaccine makers that are currently in Phase 3 trials might shed further light on the matter. Phase 3 trial volunteers will have to be observed for at least two months from the last shot. But some patients from Phase 1 trials were inoculated all the way back in March and April. Those patients will continue to be observed and tested, and that research could help us learn how long COVID-19 immunity lasts.