- A new coronavirus immunity study offers another promising conclusion for the future of COVID-19 vaccines.
- COVID-19 survivors mount an immune response that’s detectable in the blood some eight months after infection.
- Scientists have analyzed B cells in samples from COVID-19 survivors, which are white blood cells that remember previous infections and can spawn additional neutralizing antibodies when reinfection occurs.
AstraZeneca and Oxford announced interim data for their coronavirus vaccine candidate on Monday, making it the third vaccine out of three that were proven effective in Phase 3 trials. The Oxford vaccine might not have an efficacy rating as high as Pfizer or Moderna, but the drug has a few advantages. Not only is it cheaper to produce, but it can also be stored and transported at higher temperatures, making it ideal for use in places that lack the logistics needed for the other two drugs. The mRNA vaccines require temperatures well below freezing.
Vaccines alone will not end the pandemic, especially if the protection they offer wanes off quickly. The longer the immunity, the easier it will be for the world to get past COVID-19 and downgrade the illness from pandemic to endemic. In the past few months, a series of coronavirus immunity discoveries made it clear that immunity can’t be measured by looking at antibodies alone. The life of the proteins that can neutralize the virus isn’t indicative of COVID-19 immunity duration. And on Monday, the world got just the kind of coronavirus immunity announcement it needs now that it’s increasingly clear that vaccines work. A team of researchers from Australia published the world’s first study that says COVID-19 immunity can last up to eight months.
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The best coronavirus immunity study so far was released a few days ago. Researchers studied four components of the immune response to the infection with the novel pathogen in nearly 200 patients. After analyzing neutralizing antibodies, two types of T cells, and B cells for each individual, they concluded that the coronavirus immunity might last for years rather than for just a few months.
The team found that the levels of neutralizing antibodies were durable, with modest declines over six to eight months after infection. The T cells showed a minor decay, and the number of B cells actually increased in some patients.
Both B and T cells are lymphocytes or white blood cells that respond to infections. T cells can recognize and kill pathogens. B cells will remember a former enemy like the novel coronavirus and instruct the immune system to mount a new response upon reencounter. That includes the creation of a new batch of antibodies to neutralize the virus.
Researchers from Monash University, the Alfred hospital, and the Burnet Institute published similar COVID-19 immunity findings.
The researchers studied 25 COVID-19 patients, taking 36 blood samples from Day 4 post-infection to Day 242 post-infection. They found that antibodies against the virus started to drop after 20 days. But all patients continued to have memory B cells that recognized one or two components of the novel coronavirus, including the spike protein and the nucleocapsid proteins. These key components of the virus are targeted by neutralizing antibodies.
“These results are important because they show, definitively, that patients infected with the COVID-19 virus do in fact retain immunity against the virus and the disease,” Associate Professor Menno van Zelm said in a statement. “This has been a black cloud hanging over the potential protection that could be provided by any COVID-19 vaccine. Our results give real hope that a vaccine or vaccines, once developed, will provide long-term protection.”
The spike protein of the virus is of particular importance, as that’s the component that vaccines also target. Vaccines will teach the body to react to the spike protein, and the immune system should develop the same overall response (antibodies, T and B cells) that COVID-19 survivors develop. The difference is that vaccinated patients will not actually go through the illness. But their bodies will still mass-produce the antibodies and white blood cells that will recognize the actual virus in the future. The B and T cells are of particular importance, as they have a much longer life than antibodies.
The study is available in pre-review form at this link and will surely benefit from even more research.