CLINICAL MATTERS
DR. EDSEL SALVANA
What a wonderful holiday season we just had. Face-to-face gatherings are once again the norm after two years of keeping to our own households, and celebrations have been on par or exceeded pre-pandemic festivities. The fireworks on New Year’s Eve were as noisy as ever, as if to exorcise the lingering threat of Covid-19.
Even as the word braces for the inevitable surge of cases from China, the threat of a new global wave is significantly diminished. Unlike the first wave of cases that devastated Wuhan and sparked a global crisis, the latest wave of Covid-19 from China this time around will find a world with high rates of vaccination and hybrid immunity. It will find many countries well-prepared with adequate test kits, PPE, and effective medications. Most countries are not even bothering to shut down their borders, and only a handful have initiated pre-departure testing.
The Philippines through the Department of Health has reiterated its mitigation measures against imported Covid-19 cases, including those from China. Lest we forget, China is not the only country with ongoing high rates of Covid-19 community transmission. Japan was hitting 200,000 cases a day in the last week of 2022, with the US and South Korea hitting tens of thousands of daily cases in that time period. Ironically, it is these same countries that are instituting mandatory pre-departure testing for Chinese travelers when their levels of community transmission are a higher threat to their populations than the relatively small number of Chinese travelers who arrive at their borders. Moreover, high vaccination rates along with widespread hybrid immunity in these countries means that incoming cases are unlikely to cause a large increase in severe cases or hospitalization. Finally, even with breakthrough cases, vaccinated people are less likely to transmit due to lower viral loads and shorter times of illness.
From a purely scientific standpoint, there is no compelling reason to either selectively screen Chinese travelers or to quarantine them. Testing Chinese travelers won’t really do much vis-a-vis the enormous amount of domestic transmission occurring locally. Even if 10,000 infected Chinese were to come in undetected, the 200,000 infectious people a day in Japan far outstrip that threat, considering many of those domestic infections had been in close contact with others before the test became positive while the Chinese travelers would just be coming in.
In addition, testing Chinese travelers at pre-departure only in an ongoing epidemic in acceleration phase will miss a lot of recently infected cases. If these countries were serious about keeping infection out, this must be coupled with quarantine and post-arrival testing. Otherwise, pre-departure testing alone is not going to have much of an impact. The type of testing would also matter. Antigen testing will miss a lot of incubating cases while an RT-PCR will also detect convalescent cases who are no longer infectious and would not need to be isolated anyway. It would be merely perfunctory optics rather than a real attempt to cut transmission if that was truly the objective.
High rates of vaccination in most countries already means that those who have breakthrough infection are also less likely to transmit due to lower viral loads. This was the original rationale behind removing the testing requirement for fully vaccinated travelers. Most countries have removed testing requirements for everyone regardless of vaccination status. The Philippines, however, has maintained testing and quarantine measures for travelers who are not fully vaccinated. This is yet another layer of protection that is risk-based and scientifically sound. We were recently able to detect eight Filipino travelers from China with arrival testing because they were not fully vaccinated. These persons are currently undergoing required isolation and monitoring. Their viruses will likely undergo sequencing to determine if they are harboring any possible variants of concern.
So rather than singling China out for pre-departure testing that is not going to move the needle much, here is what countries that wish to mitigate Covid-19 risk should do.
- Encourage masking or bring back mask mandates, especially for vulnerable populations. The impact of travel restriction with highly vaccinated populations on transmission is miniscule compared to universal masking. If decreasing transmission is the true goal, then the one thing that will have the biggest impact on these is to reinstate mask mandates. The US CDC recently reversed its reluctance to recommend masks anew by doing so amid a “tridemic” of Covid-19, RSV, and influenza.
- Enhance boosting programs and deploy bivalent boosters as soon as they become available to the most vulnerable populations. Recent data shows that, compared to monovalent boosters, bivalent booster increase protection against severe hospitalization by more than 50 percent against the Omicron variant. Since the prevailing variant globally is Omicron and its descendants, increasing boosting with bivalent vaccines, especially among the elderly, will further enhance protection in the event of a new spike in cases.
- Do stricter symptom screening for all countries (not just China) and test on site anyone who is symptomatic at the time of travel. While it is understood that Covid-19 can be transmitted by asymptomatic persons, symptomatic people shed higher levels of virus, especially if they are actively coughing and sneezing. With the removal of mask mandates in many places, symptom screening can help mitigate transmission. If testing is not acceptable, asking symptomatic passengers to at least wear a mask can further attenuate the risk of an outbreak.
- If the decision is made to implement pre-departure testing despite its imperfections, it needs to be not just for China but for any country that has high rates of community transmission. It also needs to be coupled with quarantine and post-arrival testing if it is to have a significant effect. At this stage of the pandemic, where vaccination is widespread and there are effective treatments, this kind of draconian measure is very difficult to justify and too disruptive.