A: Yes. A well-fitted mask can provide good protection for the wearer (though two-sided masking remains most effective).
We know that plans to drop mask mandates in many schools have many parents of unvaccinated children on edge, especially with the rise of the more transmissible Delta variant.
While we encourage parents to communicate concerns they have with their schools, we know these policies are often out of parent’s control.
We also know it may be hard to expect younger children to continue masking if that’s not the norm around them. But for kids who are willing and able to mask up, they can still reduce their risk (and every little bit counts).
We know that masking is very effective at “source control”- reducing the outward flow of virus particles from an infectious individual.
But since the pandemic started, we also have new evidence on the “inward” efficiency of masks in blocking particles.
Remember the key features of effective masking: 💥FILTERING and FIT💥.
A U.S. CDC experimental study tested ways to improve mask fit for cloth and medical masks to reduce leakage around the edges.
Using mannequin “headforms” and simulated moderate breathing in a small chamber for 15-minute periods they tested:
1) Cloth mask over a medical mask (double masking)
2) Medical mask with knotted ear loops and tucked in sides.
The experiment was able to test both source control (how well the masks blocked outward coughing) and exposure for the “receiver” breathing in aerosols.
Reductions in “receiver” aerosol exposures:
💥UNKNOTTED MEDICAL MASK: 7.5% reduction
💥KNOTTED/TUCKED MEDICAL MASK: 64.5% reduction
💥DOUBLE MASK: 83% reduction
➡️ These experiments provide evidence that FIT can greatly improve the effectiveness of any mask you are wearing.
➡️ They also suggest that good fit can provide reasonable levels of protection for the wearer even if others are not wearing masks (but note that protection from the loose-fitting mask was low).
🤔 Caveats: While the experiment was designed to mimic conditions for transmission, it did not use real people or real virus (thankfully we are not allowed to such experiments). Thus, these numbers should be interpreted as a good indication of the ability of the masks to block particles of the size that carry SARS-CoV-2, but not precise measures of transmission itself. These experiments might also not mimic being in a classroom for long periods of time with an infectious individual.
While the study described was focused on improving fit of medical masks, masks with good built in filtration and fit such as KN95s are also a good choice.
Nerdy Girl mask ranking:
2️⃣ KF94 (Korea), FFP2 (Europe)
4️⃣ Double-mask (cloth mask on top of surgical, OR cloth mask with filter insert)
5️⃣ Surgical/Medical mask
6️⃣ Good fitting cloth mask
Options 1-4 provide both good filtration AND fit; besides the gold standard fitted N95, differences among these will be small so use what’s available & fits you.
Option 5: good filtration but gaps
Option 6: good fit but less filtration
We know parents are struggling to assess the risk to unvaccinated kids going back to school this fall. There will be so many different local contexts in terms of vaccination coverage, transmission levels, and mitigation measures, that a one-size fits all answer is unlikely. We’re here to try to help parents navigate this blurry and unsettling landscape.
While public health doesn’t work well as an individual-only responsibility, choosing to wear a mask even when others aren’t can still provide you or your child with protection. Social norms matter too, so your child’s choice to wear a mask could make it easier for others to do so as well.
🧀 As we’ve emphasized for many months, each layer of protection is imperfect, but stacked together like Swiss cheese they are much stronger. Children remain at low risk from serious COVID disease. Many schools have improved building ventilation during the pandemic and may employ other mitigation measures like regular testing. If even *some* students continue to wear masks when not required, this still adds another layer to the Swiss cheese defenses.