The US CDC announcement was bold, but disconcerting

Dr. Edsel Maurice T. Salvana

It came out of the blue. The US CDC announcement that vaccinated individuals were no longer required to wear masks was as bold as it was disconcerting. This followed a previous announcement that masks were not required for vaccinated people outdoors. Many in the medical field still felt that indoor masking was necessary until more data was available. The lifting of indoor masking for those who have completed their vaccination series is a giant leap of faith, and many are a bit confused after the WHO just updated guidance on potential COVID-19 aerosol transmission indoors. What is the science behind the advisory, and is it applicable to the Philippines?

The CDC’s latest advisory is based on recent studies that show COVID-19 vaccines give protection from severe disease and decrease the likelihood of onward transmission. All current vaccines are already known to protect against severe disease, and so removing one’s mask once fully vaccinated may not be all that risky for the vaccinated individual. Even if there is a rare breakthrough infection, it will most likely be mild or asymptomatic. The bigger question is the risk of transmitting the virus to others. The transmission blocking ability of vaccines was not formally measured in the original clinical trials.

New studies have now verified that vaccination substantially decreases the risk of transmission of COVID-19. Real world studies are confirming or even exceeding vaccine efficacy estimates from clinical trials for preventing symptomatic infection. One prospective cohort of healthcare workers who self-collected weekly swabs regardless of symptoms showed that mRNA vaccines were 80 percent effective at preventing infection with a single dose, and 90 percent effective after two doses. Only 11 percent of the participants were diagnosed with asymptomatic infections, and the vaccine clearly decreased the risk of asymptomatic infections as well. This reinforces the notion that the vaccines do not only prevent symptomatic infection, which was what most clinical trials measured, but also asymptomatic infections, which also have the potential to transmit. Asymptomatic transmission has always been seen as the hardest to prevent. It distinguishes COVID-19 from other coronavirus infections, which only transmit when patients are symptomatic. Another study out of Israel showed that breakthrough infections in vaccinated patients were rare and had much lower viral loads than unvaccinated individuals. Lower viral loads translate to lower infectiousness. A person infected by someone with a low viral load is also less likely to develop severe disease.

This data was enough for the US CDC to understand that vaccinated persons have very little risk of bad outcomes or of transmitting COVID-19 to others. There are, however, still more than a few unknowns. After more than a year of masking up, it can be very disconcerting to remove an item that has become a part of life during a pandemic. There are still questions lingering on the effectiveness of the vaccines against the new variants. More and more data suggest that most vaccines work well against the new variants to at least prevent severe disease.

While the US may feel justified in relaxing measures since they have already inoculated a substantial proportion of their population, many less developed countries, including the Philippines, are still in the early stages of vaccination. There are still a substantial number of people locally who are not vaccinated, including children.

An important benefit of the decreased risk of transmission from vaccination is that more countries are starting to relax their quarantine policies for vaccinated persons arriving from overseas. These initially included relaxing testing requirements and shortening quarantine times for fully vaccinated travelers. Saudi Arabia and Germany have taken the full leap in now allowing vaccinated travelers entry from certain countries with no further need for quarantine or testing. More countries are expected to follow suit. This will jumpstart the return of business and leisure travel and will substantially decrease the cost of having to test and quarantine all travelers coming in and out of a country. This will also ease deployment and repatriation of overseas Filipinos.

One big concern for relaxing quarantine and masking requirements is the type of vaccine used. While the mRNA vaccines Pfizer and Moderna are clearly transmission blocking, what about the other vaccines used around the world? Will a country only recognize vaccines that are approved by its FDA or equivalent? There is more and more data that non-mRNA vaccines, particularly Sinovac and Astra, are also very good at blocking transmission. The US has stated that as long as a vaccine has WHO Emergency Use Listing (EUL), it will recognize the vaccine and no longer require the traveler to be reinoculated.

With Germany taking the lead, the Schengen countries are expected to relax travel restrictions for vaccinated travelers as well. There are, however, still no specific policies on which vaccines are covered. China initially preferred that travelers be inoculated with Chinese vaccines prior to being granted visas but has now agreed to accept visa applications from travelers who received vaccines made in the US. It is expected that most countries will recognize vaccines with a WHO EUL. The current vaccines as of this writing that have WHO EULs are Astra, Janssen, Sinopharm, Pfizer, and Moderna. A decision on Sinovac is expected before the end of May, while the other vaccines including Indian and Russian made vaccines are in various stages of evaluation. Almost all of these vaccines, possibly all of them, are expected to get WHO EUL as long as they meet the required parameters.

When the Philippines does eventually decide to decrease measures for quarantine and masking, there are a few logistical hurdles that need to be worked out. The issue of fake vaccine certificates, just like fake RT-PCR results, is always a challenge. Electronic verification will likely be the quickest solution. An internationally recognized system akin to the yellow cards for Yellow Fever vaccination may be used and can greatly facilitate domestic and international travel. It also needs to be clear that fully vaccinated means being at least two weeks out from the second vaccine dose, except for the single shot Janssen vaccine, which kicks in in two to six weeks. Right now, the biggest challenge is vaccine supply and a quick rollout. With the accelerating arrival of millions of vaccine doses in the next few months, getting everyone vaccinated as quickly as possible will be the fastest way out of the pandemic. As cases and deaths drop, the chances of having mask-free Christmas parties are looking good, as long as we all do our part and get our shot

#US CDC

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