Here’s Why Vaccinated People Still Need to Wear a Mask

New York Times ^ | December 9, 2020 | Apoorva Mandavilli

[ProtectOurFreedom]

The new Covid-19 vaccines from Pfizer and Moderna seem to be remarkably good at preventing serious illness. But it’s unclear how well they will curb the spread of the coronavirus.

That’s because the Pfizer and Moderna trials tracked only how many vaccinated people became sick with Covid-19. That leaves open the possibility that some vaccinated people get infected without developing symptoms, and could then silently transmit the virus — especially if they come in close contact with others or stop wearing masks.

If vaccinated people are silent spreaders of 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. “It’s really going to be critical for them to know if they have to keep wearing masks, because they could still be contagious.”

In most respiratory infections, including the new coronavirus, 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.

[ProtectOurFreedom]

There was a recent randomized controlled trial of mask wearing in Denmark:

Danish Study Casts Doubt Surgical Masks Protect Wearers from Coronavirus, by James Delingpole, 20 Nov 2020:

According to the DANMASK-19 study, published in the prestigious journal Annals of Internal Medicine, there was no statistically significant difference between the mask-wearing group and non-mask wearing group’s likelihood of becoming infected with COVID, as measured by antibody testing, hospital diagnosis, and PCR testing.

Here is the study’s key finding:

Our results suggest that the recommendation to wear a surgical mask when outside the home among others did not reduce, at conventional levels of statistical significance, the incidence of SARS-CoV-2 infection in mask wearers in a setting where social distancing and other public health measures were in effect, mask recommendations were not among those measures, and community use of masks was uncommon. Yet, the findings were inconclusive and cannot definitively exclude a 46% reduction to a 23% increase in infection of mask wearers in such a setting. It is important to emphasize that this trial did not address the effects of masks as source control or as protection in settings where social distancing and other public health measures are not in effect.

The study, conducted in Denmark in April and May this year, is the largest randomised controlled trial on the efficacy of masks against COVID-19 infection.

A total of 3030 participants were randomly assigned to the recommendation to wear masks, and 2994 were assigned to control; 4862 completed the study. Infection with SARS-CoV-2 occurred in 42 participants recommended masks (1.8%) and 53 control participants (2.1%). The between-group difference was −0.3 percentage point (95% CI, −1.2 to 0.4 percentage point; P = 0.38) (odds ratio, 0.82 [CI, 0.54 to 1.23]; P = 0.33). Multiple imputation accounting for loss to follow-up yielded similar results. Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection.

What this means is that the results are inconclusive. Fewer mask-wearers ended up catching Covid than non-mask wearers. But not enough to demonstrate convincingly that masks make any real difference preventing the spread of Covid. Study limitations included reliance on patient-reported data (on mask behaviour and results of home antibody tests), inability to blind study participants to the intervention, and loss of patients to follow up.

[JerryBlackwell]

Remember a day without a Mexican? Lets do a day without a mask where all 70 million Trump voters go out unmasked.

[Wuli]

Yes, it was a Chinese study, but it is a study that has been reviewed by others who do epidemiology studies.

It is reinforced in my mind by a recent New York State study that found 74% of Wuhan Virus infections were not passed out in the open society; they were passed in the home. And the other single largest %, nearly 8%, were passed in institutional settings such as health care facilities and nursing homes. That status showed nearly 82% of infections were NOT passed out in the open society. If “secret” asymptomatic virus spreaders were as prevalent as the false guessers claim the New York state study could not have demonstrated the numbers if did show - MOST infections incur in (a) closed settings, (b) with close contact, (c) over a period of time. Short term and random public encounters with asymptomatic persons are not any part of any “surges”.