Isolation, quarantine, and what it means in the age of Omicron and Delta

CLINICAL MATTERS

Many people, including doctors, were puzzled by the recent changes made by the US Centers for Disease Control (CDC) to the duration of quarantine and isolation. The CDC shortened both quarantine and isolation periods amid its largest spike in cases driven by Omicron. What is the rationale for these changes, and should these be applied in our country as well?

To answer these questions, it is useful to review basic terminology. Quarantine and isolation are often used interchangeably, but they are not the same. 

Quarantine refers to the restriction of movement for a person who has been potentially exposed to a disease but is not yet showing any symptoms. Some people in quarantine may never develop infection or test positive. Some people who are incubating the disease eventually develop the disease and test positive. The purpose of quarantine is to pre-emptively prevent infectious people from exposing others. People with high-risk exposure or close contact with known COVID-19 cases (cumulative 15 minutes within three to six feet without medical grade PPE) should quarantine. The typical length of a quarantine period is the upper limit of the incubation period of a disease, in this case 14 days.

Incubation period refers to the amount of time it takes to develop symptoms from the time a person is infected with a pathogen. For COVID-19, this is typically three to five days from the initial exposure, but can take up to 14 days. This is why quarantine periods for people exposed to a positive COVID-19 case have been traditionally 14 days, because most people who were exposed would be expected to develop symptoms before the end of the quarantine period. If the exposed person does not develop symptoms by the 14th day from exposure, it is unlikely that person is infected. If they do develop symptoms, the clock starts anew and the isolation period begins.

Isolation period refers to the amount of time someone with known infection needs to be isolated to become non-infectious. For COVID-19, this is typically 10 days from the start of symptoms. If someone is completely asymptomatic, the count starts from the date of the first positive test. For people who are hospitalized with severe or critical COVID-19, the isolation period is set for longer at 21 days because these patients can shed infectious virus longer.

The new US CDC guidelines recommend cutting the quarantine period for unvaccinated individuals from 14 days to only five days, with testing recommended on the fifth day and strict mask use for another five days as long as they remain asymptomatic or are afebrile for at least 24 hours. The same holds true for fully vaccinated individuals who are more than six months from their second dose of vaccine (two months from Janssen dose) with exposure. For fully vaccinated individuals less than six months from the second dose, or those who have been boosted, there is no need to quarantine but a fifth day test is recommended and strict mask use for 10 days from the date of exposure. The rationale for this change is that the newer variants Delta and Omicron typically manifest symptoms faster than previous variants of SARS-CoV-2 and almost all patients will turn positive, even if asymptomatic, by the fifth day. The testing in these guidelines, however, is recommendatory and not compulsory, which can be problematic since up to 40 percent of Omicron is thought to be asymptomatic.

Current Philippine guidelines recommend 14 days quarantine for unvaccinated individuals with close contact. For fully vaccinated individuals, quarantine is seven days, with a test on the seventh day after which they can be released if the test is negative, but with close monitoring and strict mask use for seven more days. No distinction between boosted and non-boosted individuals has been made at this time. 

Adopting the more relaxed US guidelines for quarantine locally may be considered, especially in areas with high vaccination rates. Since most local community transmission is Delta at this time, the shortened time frames will capture most cases. The testing on the fifth day, however, should be compulsory and not voluntary, especially since there will likely be community transmission of Omicron very soon. 

The US CDC guideline cutting isolation for confirmed cases is more problematic. From 10 days, they cut the isolation time to five days from the start of symptoms, provided the patient is asymptomatic. No repeat testing is needed. The patient must strictly use a mask for five more days afterward. This is regardless of vaccination and boosting status. The rationale for the change is that recent data shows that most transmission occurs in the one to two days before the onset of symptoms, as well as the first three days of symptoms. 

The shortened isolation period is not advisable for the Philippines at this time. There is still a lot that is not yet known about Omicron, and there is still a lot of Delta around. Delta has very high viral loads and it may take more than five days to become non-infectious. Moreover, the high number of asymptomatic and minimally symptomatic Omicron patients may make it difficult to keep track of the onset of symptoms, and people may minimize any residual symptoms. If there is one qualifier that can be considered in shortening isolation, it may be being fully vaccinated. A recent study showed that the viral load of fully vaccinated individuals with breakthrough infection from Delta was approximately 10 times lower than in unvaccinated individuals. It is still too early to extrapolate this to Omicron and shortening our isolation period for confirmed COVID-19 cases may be premature at this time.

Now that cases are increasing anew, it is important to increase adherence to our public health standards. Shortening quarantine and isolation periods will increase the risk of a miscalculation, especially with the looming threat of Omicron. In this new year, the country is in a better place than last year. Active cases in 2021 remain lower than the previous year, nearly 50 million Filipinos are fully vaccinated, and effective treatments are available. Vaccines continue to work in preventing severe disease. Everyone knows what to do to mitigate the impact of an Omicron wave. Keeping each other’s safety in mind will allow a safer 2022 and ensure that this will be the last year of the pandemic.