Corona vaccination : Vaccinated adults can protect children from Covid-19
Unvaccinated children appear to be benefiting from mass Covid-19 vaccination programs in many parts of the world. In many places, infections in children have declined while adults received their vaccinations. However, experts disagree on whether this means that unvaccinated children do not become a reservoir for infection and a potential breeding ground for the emergence of new variants.
The answer affects whether children in wealthy countries should be prioritized for vaccination or whether doses should go to poorer countries instead.
Impressive data on how adult vaccination affects children comes from the small town of Serrana in the Brazilian state of Sao Paulo, where 98 percent of adults have been vaccinated. The city was the site of a unique experiment – called Project S – to measure CoronaVac’s real-world effectiveness. The drug had been developed by Beijing-based pharmaceutical company Sinovac. Compared to other vaccines, Sinovac had been less successful in preventing symptomatic infections in some previous clinical trials, with efficacy rates as low as 50 percent.
But in early June 2021, a team from the Butantan Institute in the city of Sao Paulo reported a remarkable decline in Covid-19 cases and deaths at a press conference: Symptomatic cases dropped by 80 percent and deaths by 95 percent. Only 62 percent of Serrana’s 45,000 residents are adults, but a similar decline in symptomatic infections occurred in unvaccinated children, says Ricardo Palacios, the epidemiologist who led the study.
"It was one of our fears that if you vaccinate everyone else, the disease will cluster in children and adolescents," he says. "But we didn’t see that."
Do mass Corona vaccinations provide herd immunity?
Similar scenarios have played out in countries with high vaccination rates, such as Israel and the United States. In the latter, cases among children – generally those under 18 – declined by 84 percent between January and May. Slightly more than half of the U.S. population – mostly adults – had received at least one vaccine dose.
In Germany, about 22 million people are fully vaccinated as of mid-June. That represents just over 26 percent of the total population, according to the vaccination dashboard. Overall, by 14. By June 2021, more than 40 million people, about 48 percent of the population, will have received at least one vaccine dose. While the figures vary by state, there is a clear age distribution: among those vaccinated, the majority are people over 60 years old, followed by those 18 to 59 years old. That’s according to a recent report from the Robert Koch Institute (PDF). Example: In Baden-Wurttemberg, Germany, 79.1 percent of all people over 60 are vaccinated, 44.4 percent of those 18 to 59 are vaccinated, and 1.6 percent are younger than 18 years old. In Lower Saxony, the comparative breakdown is as follows: 83.6 percent, 42.1 percent, 1.1 percent (as of 14. June 2021).
The procedure "makes sense," says Monica Gandhi, an infectious disease physician at the University of California at San Francisco. Vaccination of adults protects those who are not vaccinated. "This is what herd immunity really means," she says. Children are also less likely to transmit the virus than adults, he said – another reason why they might not act as an effective reservoir for infection. "The way the virus affects children is just different," she says, probably because children’s respiratory tracts have fewer of the receptors that Sars-CoV-2 uses to enter cells.
In Israel, infection rates among those eligible for vaccination have plummeted, from 559 cases per 100,000 people aged 16 and older in mid-January to just 1.5 per 100,000. Most schools reopened in March. Rates also fell among unvaccinated children, for example from 546 per 100,000 to 1.5 per 100,000 among those under 11 years old.
Increased numbers of children and adolescents in Germany have contracted Sars-CoV-2 in early 2021. The peak was reached in calendar week 16. At that time, more than 33,000 people aged 0 to 19 years were officially infected, according to an RKI report. In the 12- to 19-year-old age group – now also eligible to be vaccinated – there were about 19,000 cases in the week in question. Numbers have been steadily dropping since the peak.
Unvaccinated children could continue to be significant Corona carriers
The numbers in Israel suggest that children are most often infected by adults, says Eric Haas, an infectious disease pediatrician and epidemiologist at Israel’s Ministry of Health in Jerusalem. "Otherwise, when children go back to school, they would be expected to infect each other en masse."
But not everyone reads the data this way. Julian Tang, a virologist at the University of Leicester in the U.K., says the speed with which vaccination was carried out in Israel may have contributed to its eradication of infections in all age groups. "By the time adult vaccination was complete, there was no longer a source of infection to carry the virus into schools, he says.
In the United Kingdom, the vaccination rate is currently 60 percent. Early data from there also paint a more complicated picture when it comes to unvaccinated children and their potential to spread Covid-19. By the end of May, cases in secondary school children in England had dropped from a high of about 600 cases per 100,000 in January to fewer than 100 per 100,000. Numbers are now even lower among younger school children there.
But recent data also suggest that unvaccinated children could still be significant carriers of the virus. In May, there were nearly 100 outbreaks – defined as two or more cases – in primary and secondary schools in England. "However, this number is small and represents only a tiny proportion" of the country’s 25,000 schools, says Shamez Ladhani, a pediatric infectious disease physician at Public Health England. It also notes that overall infection rates among school-age children have changed little in the six weeks since schools reopened.
Still, Tang says transmission in schools should not be ignored. The reopening of schools coincided with the increasing prevalence of B.1.617.2 – also known as the delta variant – in UK communities together. As a result, the virus could continue to circulate among children. This is an important point, Tang says. That’s because the longer the pandemic lasts, the greater the chance that new variants with some resistance to vaccines will develop, he said.
Just under one percent of those under 18 vaccinated nationwide
In the United States, the Federal Drug Administration announced on 10. May 2021, Biontech/Pfizer’s vaccine was approved for children ages 12 to 18, and more than seven million of those children have now received at least one dose. Authorities in the European Union, Japan, the United Kingdom, and elsewhere have now also granted approval.
In Europe, the European Commission had approved Biontech/Pfizer’s vaccine for children 12 years and older at the end of May, on the recommendation of the European Medicines Agency (EMA). Meanwhile, the Standing Commission on Vaccination in Germany has not issued a general vaccination recommendation for healthy children and adolescents 12 years and older. It recommends vaccination against coronavirus only for 12- to 17-year-olds with certain preexisting conditions and those with relatives or other contacts at high risk for a severe covid 19 course. Slightly more than one percent of people under 18 in this country have already received their first vaccination dose, according to the RKI’s digital vaccination rate monitoring, as of 14. June 2021 shows.