Can COVID-19 vaccines bring the pandemic under control?

An Australian study has indicated the COVID-19 vaccine-induced immunity can last for at least 8 months. And experts say this is enough time to bring the pandemic well under control, if not eradicated altogether.

Given the urgent need to find ways to stop the ongoing coronavirus pandemic, which has claimed 1.7 million lives since it started last year in China, vaccines are being developed, tested and introduced in a short span of time across the world. Some countries have already started vaccinating its people in the hope to protect them form the deadly virus and stop the outbreak. But one question remains debatable can COVID-19 vaccines eradicate the coronavirus or at least bring the pandemic well under control?

The COVID-19 vaccines, like all other vaccines, essentially aim to train the immune system to recognize and combat the virus. "Vaccines train our immune systems to create proteins that fight disease, known as 'antibodies', just as would happen when we are exposed to a disease but crucially vaccines work without making us sick," as described by the World Health Organisation (WHO).

According researchers, the immunity provided through vaccination is sometimes stronger than what would be provided through natural infection. Vaccination protects people from getting the disease in question and passing it on to other, and thus break the chain of transmission.

How long the immunity induced by Covid-19 vaccine can last?

The duration of natural or vaccine-induced immunity is not yet fully understood. A study, published in the journal New and Emerging Respiratory Virus Threats Advisory Group, claims that a protective immune response after SARS-CoV-2 infection or vaccination may last for up to 90 days or three months.

However, an Australian study revealed that our immune system is capable of mounting a strong response for at least eight months post-infection. Not just this finding has put to rest the concerns that people may lose their immunity to the virus quickly, but also indicated the COVID-19 vaccines can provide protection longer enough to manage the virus's spread throughout the population.

The study, published in Science Immunology, was jointly conducted by researchers at Monash University, The Alfred Hospital, and the Burnet Institute in Melbourne.

As suggested by previous studies, the Australian researchers also found that concentrations of free-floating SARS-CoV-2 antibodies begin to fade just 20 days after symptoms appear, with the drop in antibody levels more likely in mild cases of COVID-19.

However, they also found that blood samples of COVID-19 patients they studied continued to have specific white blood cells within the immune system, called memory B cells, for as long as eight months post infection.

According to the researchers, these memory B cells can remember infection by the virus and trigger a protective immune response if re-exposed to the virus.

Based on this finding, the researchers opine that most vaccines will also convey a good level of immunity for at least eight months.

70% population should be immune to the virus to control the pandemic

The pandemic can be brought well under control, if not eradicated altogether, if at least 70 percent of a population become immune to the virus within the same window of time (eight months). When it's done, the virus will have few places to hide, and gradually it just might vanish, say experts.

Not just the new study has given hope to the efficacy of COVID-19 vaccines, but also explains why there have been very few cases of coronavirus reinfection globally.

"This has been a black cloud hanging over the potential protection that could be provided by any COVID-19 vaccine and gives real hope that, once a vaccine or vaccines are developed, they will provide long-term protection," said study co-author Menno van Zelm, from the Monash University Department of Immunology and Pathology.

"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," van Zelm added.

But WHO chief says a vaccine will not be enough to stop coronavirus pandemic. "A vaccine will complement the other tools we have, not replace them. A vaccine on its own will not end the pandemic," WHO director-general Tedros Adhanom Ghebreyesus had said last month.

As supplies of the vaccine would initially be restricted to high risk population, the virus will have a lot of room to move. Therefore, he recommended that surveillance, testing, isolation, contact tracing and other COVID-19 protocols should be continued.