Explained: Why people vaccinated against COVID-19 still need to wear mask?

New Delhi, Dec 09: The vaccine for the novel coronavirus from Pfizer and Moderna seem to be remarkably good at preventing serious illness. But, it is unclear how well these vaccines would curb the spread of the coronavirus.

This is because Pfizer and Moderna trials tracked only how many vaccinated people fell sick with COVID-19. This leaves open to the possibility that some vaccinated people may get infected without developing symptoms and could then silently transmit the virus.

If vaccinated people are "spreading the virus", they may keep it circulating in their communities, putting unvaccinated people at risk.

"A lot of people are thinking that once they get vaccinated, they're not going to have to wear masks anymore," said Michal Tal, an immunologist at Stanford University.

In most cases related to respiratory infections, including the new coronavirus, it can be seen that the nose is the main port of entry. The virus rapidly multiplies there, jolting the immune system to produce a type of antibodies that are specific to mucosa, the moist tissue lining the nose, mouth, lungs and stomach.

If the same person is exposed to the virus a second time, those antibodies, as well as immune cells that remember the virus, rapidly shut down the virus in the nose before it gets a chance to take hold elsewhere in the body.

In contrast, the coronavirus vaccines are injected deep into the muscles that are absorbed into the blood, where they stimulate the immune system to produce antibodies. This appears to be enough protection to keep the vaccinated person from getting ill.

Some of those antibodies circulate to the nasal mucosa and stand guard there. However, it is not clear how much of the antibody pool can be mobilized or how quickly. If the answer is not much, then viruses could bloom in the nose - and be sneezed or breathed out to infect others.

The vaccines have proved to be powerful shields against severe illness, but that is no guarantee of their efficacy in the nose. The lungs, the site of severe symptoms, are much more accessible to the circulating antibodies than the nose or throat, making them easier to safeguard.