What to expect with Omicron

Published December 21, 2021, 12:05 AM

by Dr. Edsel Salvana

Two international travelers, both asymptomatic, are the first cases of this variant

CLINICAL MATTERS

On Dec. 15, 2021, the Department of Health reported the first two cases of the Omicron variant among incoming travelers. 

The first case was a returning 48-year-old overseas Filipino male from Japan who arrived on Dec. 1, 2021 and developed mild symptoms. He was put under quarantine on arrival per protocol. Fifth day RT-PCR testing was positive for SARS-CoV-2 and the patient was transferred to an isolation facility. Currently asymptomatic, he will be kept in isolation for at least 10 days from the onset of symptoms. This is the protocol for all COVID-19 positive patients regardless of variant. Since all samples from travelers testing positive are prioritized for sequencing, his sample was sent to the Philippine Genome Center. Omicron was subsequently identified. Repeat RT-PCR testing will be done prior to release to document clearance of the virus. 

The second case was a 37-year-old male Nigerian national who arrived from Nigeria on Nov. 30, 2021. He was asymptomatic on arrival. He was put under quarantine on arrival per protocol. He was likely unvaccinated since he underwent RT-PCR on the seventh day of arrival. Unvaccinated persons get tested on the seventh day of arrival while vaccinated persons are tested on the fifth day. This came back positive for SARS-CoV-2 and he was transferred to an isolation facility. Still asymptomatic, he will be kept in isolation for at least 10 days from the date of the positive test. His sample was sent to the Philippine Genome Center, where Omicron was identified. Repeat RT-PCR testing will also be done prior to release to document clearance of the virus.

Enhanced contact tracing has been initiated for all the close contacts of these patients. Since these close contacts are the travelers on the flights the index cases took, they would have all been quarantined and tested according to prevailing protocols. They would have been contact traced at the time these two patients tested positive, even before the genomic sequencing came back for Omicron. The LGUs where these patients are completing facility or home quarantine will be monitoring them for symptoms. The LGUs can extend quarantine and do repeat testing as needed, and transfer persons who test positive to isolation. The Philippine Genome Center will sequence samples from any positive tests from the close contacts.

The detection of these two cases means that our country’s genomic surveillance and border control is working. Both travelers were in quarantine when they tested positive and were isolated in accordance with health protocols. Community transmission was therefore prevented. With Delta, there was a two-month delay in entry into the community from the time it was first detected in returning seafarers. Strict border control slows down the entry of variants of concern and gives a country time to prepare.

In the event Omicron makes it into the community, transmission is expected to be faster than Delta. While there is some data that it may cause milder disease, higher numbers of people getting sick can still overwhelm healthcare systems. In order to prevent overloading of the healthcare system, vaccination is essential to decrease the proportion of people who develop severe disease. Continued use of face masks and the addition of face shields further decrease transmission.

Early data shows that while antibody activity against Omicron is significantly decreased for all vaccines, the protection that vaccines provide against severe disease and death remains. This is due to continued protection from the cell-mediated arm of the immune system, which includes T-cells. Our body’s T-cells, which are stimulated by vaccination, are less affected by mutations in the SARS-CoV-2 spike protein. T-cells hunt down viruses that escape from the antibodies and destroy virus-infected cells.

Unvaccinated people are more than 10 times as likely to die if they contract COVID-19 compared with fully vaccinated people. Vaccination rates among the eligible population in Metro Manila is over 90 percent, and so there is substantial protection in these areas even if Omicron gets through.

Boosters seem to increase neutralizing antibody levels and activity. Preliminary data from Sinovac and from Pfizer vaccines show that neutralizing antibody activity against Omicron is nearly gone despite the two-dose primary series. A booster dose of vaccine is associated with some restoration of antibody activity. Mixed or heterologous booster vaccination is expected to provide similar levels of protection regardless of which brands are mixed. While higher antibody levels can provide better clinical protection, it does not mean people without a booster aren’t protected from hospitalization. Protection from severe disease continues beyond six months.

Masks are still needed for now since the decrease in clinical protection from vaccines means that herd immunity can no longer be achieved with the current batch of vaccines. The US and many European countries took their masks off too early and are now seeing large spikes in cases from both Delta and Omicron since the vaccines did not provide enough protection from clinical infection. Next-generation vaccines and modified vaccines are being developed to restore transmission-blocking properties to vaccines, but these may take a few months. Meanwhile, ensuring as many people get their primary series of vaccines will minimize severe disease in the population if an outbreak occurs. While boosters offer a temporary quick fix for decreasing susceptibility to infection, little is known about how much actual protection these add or how long the added protection lasts.

Public health protocols will continue to work as long as everyone follows them. Targeting areas with low vaccination rates and offering boosters to the most vulnerable will prevent hospitalizations and death. This Christmas season, keeping parties virtual and minimizing physical gatherings may offer additional insurance against an Omicron surge.

In high-risk areas, wearing a face shield on top of masks offers an extra layer of protection, especially indoors and in crowded settings. Since Omicron is projected to be more contagious than Delta, every little bit helps. The positive aspect to all this is that the country is in a much better position now than during the Delta wave, or at any other time before vaccination was available. Case numbers are currently very low, people are wearing their masks, and the vaccination efforts are bearing fruit. If Omicron does eventually make it to the community, it can be beaten with careful preparation and everyone’s cooperation.

 
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