Are we endemic yet?
CLINICAL MATTERS
Six hundred thousand new Covid-19 cases in one day in South Korea! Nearly 300,000 in Germany! Almost 200,000 in Vietnam! These numbers almost sound made up. Unimaginable. While many people were apoplectic at the nearly 39,000 cases we had in January 2022, the numbers from Omicron in other countries continue to skyrocket. The Philippines in the meantime has stayed at under 1,000 cases a day since March 2, 2022. Many of the countries showing large numbers of cases do have high vaccination rates. Vietnam is nearly 80 percent fully vaccinated and 45 percent boosted. South Korea is 86 percent fully vaccinated and 63 percent boosted. These two nations and many other countries still have mask mandates.
So what happened that we are so blessed? Are we just undercounting cases? For sure, no country has captured every single case of Covid-19. Not everyone who gets sick will test. Even if someone does a test, the accuracy of the tests aren’t 100 percent so some cases will still be missed. One of the best indicators of adequate testing is positivity rate. The World Health Organization says that a positivity rate of five percent over a period of two weeks is adequate testing during the acute phase of the pandemic. Our positivity rate has been below five percent since the end of February 2022 and so we are very well into the adequate testing phase.
So, if these low numbers are real, what made it possible? The reasons are likely multifactorial and are a product of both science and luck. Among these factors are:
- People are religiously following mask mandates.
Filipinos, in general, have worn their masks faithfully, and there is wide support for retaining mask mandates. Face shields likely helped, especially when vaccination was just starting. Some people continue to wear them on top of their masks. Even now, people still feel naked without their masks when eating out. We see people putting their masks back on when they go to get food in buffets. This continued compliance with mask mandates gives us an extra layer of safety and has so far attenuated sustained outbreaks.
- We have many vaccine types.
Most countries only use a handful of vaccine brands. The US for instance only has two mRNA vaccines (Pfizer, Moderna) and one viral vector vaccine (Janssen). With the rise of the variants of concern, too much emphasis on the spike protein as a vaccine target increases the risk of antigenic (the part of the virus that the immune system binds to) escape. We use eight different brands in the Philippines. Despite the Western bias against Chinese brands, the inactivated vaccines (Sinovac, Sinopharm) have more antigen epitopes (parts of the virus that induce immune responses) on top of the spike protein. This makes these vaccines more likely to be resilient against variant mutations.
- Early boosting at three months.
The Philippines was one of the earliest countries to adopt boosters at three months from the second vaccine dose. A month before the Omicron wave, the All-Experts Group of the Department of Health quickly reviewed available data on vaccine efficacy, particularly from South Africa and the United Kingdom. It was shown that there was an approximately 15 percent drop in vaccine efficacy against hospitalization for Omicron compared to Delta at three months from the second vaccine dose. In anticipation of the entry of Omicron, the AEG recommends offering boosters to all fully-vaccinated persons above 18 years old. Many healthcare workers, elderly people, and those with comorbid conditions got their booster shots just in time for the Omicron spike. This resulted in low numbers of severe diseases and subsequent hospitalization. In addition, because of our vaccine brand diversity, many people ended up with heterologous (different vaccine brand from primary vaccination) boosters. There is increasing evidence that heterologous boosting may be more effective against variants versus giving a homologous (same vaccine type) booster.
- Our January 2022 Omicron spike was BA.2.
Unlike most countries in the world that got the Omicron sublineage BA.1, our January 2022 spike was BA.2 driven. The Philippine Genome Center detected BA.1 among quarantined travelers, which means these viruses didn't make it to the community. Unfortunately, someone with a BA.2 virus made it through. This resulted in a large spike of cases, which fortunately quickly receded. It ran into a boosted and recently vaccinated population. We were also able to delay our earlier Delta spike with preemptive lockdowns so the hybrid immunity (immunity from vaccines mixed with natural infection) from breakthroughs from August 2021 was still relatively fresh.
It is unclear which of these interventions had the greatest impact, but what is very clear is cases are staying low despite opening to full capacity with Alert Level 1. Our hospitals are not overwhelmed and severe and critical cases continue to drop. There may be other factors but these are the ones that make the most sense. Cases staying low and at manageable levels, coupled with continuing vaccine programs and boosting will ensure that the risk of another spike is minimal. If this continues, then Covid-19 in the Philippines is well on its way to endemicity.
Only the WHO can declare the pandemic over, but the shift to endemicity has already begun. The next steps would eventually include shifting Covid-19 hospital bed allocations to regular beds, easing of mask mandates (initially outdoor, then eventually indoor), and removal of remaining testing and quarantine protocols. Vaccination against Covid-19, including boosters and potential future doses, need to be incorporated into the healthcare system.
The lessons learned from the pandemic should not be forgotten. The strategies that worked should be codified into a pandemic preparedness plan, and structural changes should occur to make our country more resilient against future pandemics. Surveillance for existing diseases with pandemic potential, as well as for future unknown pathogens should be strengthened. In the meantime, we should not become complacent during this critical transition period. A new spike is always possible. If that does happen, we already have protocols in place to respond to it. In the meantime, enjoy your newfound freedom, but don't take it for granted. Keep masking up and vaccinating and we will be ok.