Kids are getting COVID, and with the highly infectious Delta variant still surging in the US, there are a lot of concern about outbreaks once all the children are back in school.
Of course, while some kids get very sick from COVID-19, most do not, thankfully. But kids tend to live with adults, and so a key question is how often infected kids pass COVID-19 to other family members. And this week, appearing in JAMA Pediatrics, we get the most granular data yet answering that question.
The study comes out of Ontario, where a unified health system allowed researchers to track all known positive COVID cases on a household-by-household basis. The timeframe is important here; data ranged from June to December 2020, so we are pre-vaccine and pre-Delta variant. The researchers found 6280 pediatric index cases; that's where the first case in the household occurred in someone 17 or younger. They then checked how many people in the household tested positive for COVID within the next 14 days.
Let me start with the topline results: 27% of households with a pediatric index case had at least one other household member become infected. In any house where transmission occurred, on average two additional family members were infected.
This is interesting — an attack rate that is a bit lower than might be expected, given the lack of vaccines during the study period. But we also see that when anyone in the house got a secondary infection, often, more than one person got a secondary infection, which supports the idea that some people are just more infectious than others.
And the researchers were able to quantify that. For example, kids ages 0-3 were more likely to transmit to a household member than those aged 14-17. This could be due to biological factors, but frankly, I suspect it's just much easier for a 14-year-old to isolate himself from the rest of the family compared with a 3-year-old. And overall, the difference wasn't huge. The attack rate was about 31% if a toddler was the index case, 27% if it was a teenager.
One risk factor for family transmission really stuck out, though: the testing delay. This is the length of time between symptoms and the positive COVID test. There was a strong dose-response relationship between testing delay and the rate of household infection; the longer people had symptoms before getting tested, the more likely they were to transmit to a family member.
Those who never developed symptoms were unlikely to transmit, by the way, but it still happened about 9% of the time.
We're not in the same world as when this study was conducted. We can get vaccinated, which should significantly reduce transmission and mitigate the effects when transmission occurs. But we also have the Delta variant, which is much more contagious than the coronavirus circulating at the end of 2020. Because of Delta, we are likely to see a much greater rate of transmission among unvaccinated kids as schools open, and the household attack rate may be higher.
But rapid testing may be the key here. By identifying sick kids early, as soon as they develop symptoms, protective measures can be taken and secondary infections reduced.
F. Perry Wilson, MD, MSCE, is an associate professor of medicine and director of Yale's Clinical and Translational Research Accelerator. His science communication work can be found in the Huffington Post, on NPR, and here on Medscape. He tweets @fperrywilson and hosts a repository of his communication work at www.methodsman.com.
USEFUL INSIGHTS:
As vaccines are not approved for use in children under 12 years old and yet the transmissibility of toddlers is greatest in the study of causing up to 31% of secondary infections in households, it is thus important to
isolate your child when he/she is unwell - Symptoms include
Cough
Fever or chills
Shortness of breath or difficulty breathing
Muscle or body aches
Sore throat
New loss of taste or smell
Diarrhea
Headache
New fatigue
Nausea or vomiting
Congestion or runny nose
Do an antigen-rapid test as soon as possible if the child is suspected to have the infection; the early diagnosis will allow quick isolation as the Delta variant is known to have 1000 fold more viral load in the first 4 days of incubation and thus is highly infectious in the early stage of infection.
Ensure that all high risk patients at home those who are above 65 years and immunocompromised get vaccinated as soon as possible.
Multisystem Inflammatory Syndrome in Children (MIS-C)
Doctors at children’s hospitals in the U.S. and the U.K. have noted that children between ages 2 and 15 may experience a condition called multisystem inflammatory syndrome in children, or MIS-C after an infection with the coronavirus.
Call your family doctor or pediatrician right away if your child experiences a fever of 38 degrees Centigrade or more that lasts more than 24 hours and at least one of these symptoms:
Unusual weakness or fatigue
A red rash
Abdominal (belly) pain
Vomiting and diarrhea
Red, cracked lips
Red eyes
Swollen hands or feet
