Covid Commentary: A Plateaux?

Reaching a Plateau?

"Since Tuesday 27 July, 191 individuals have recovered and 109 new cases have been identified. 57 cases have been identified through seeking healthcare, 12 through inbound travel, 2 through admissions screening, 8 through planned workforce screening, 2 through cohort screening and 28 through contact tracing. The number of active cases in the Island is 2,871."

The number of new cases continues to decline, although the reasons are unclear. Changes in behaviour, mask wearing, being outside more in summer, and school holidays may all be driving change. 

Vaccines also are playing a significant role in reducing transmission, although they won't be fully effective until 90% of the adult population is double vaccinated, and children (where parents permit) in the 16+ age range are also vaccinated.

Studies show that asymptomatic infection can be reduced by 90% and symptomatic infections reduced by up to 96% in vaccinated people compared to those not vaccinated. This has been reduced with respect to the Delta variant.

I am pleasantly surprised that my initial predictions have proven wrong!

The mathematics suggests that if cases average 100 new cases a day, and drop out is 14 days after infection, the plateau should reduce to around 1,400 active cases.

Mask Wearing and Transmission

However, mask wearing, while not 100% effective still has an effect. A February 2021 BMJ article, "
Covid-19: Are cloth masks still effective? " noted that: "fabric face masks “blocked between 62.6% and 87.1% of fine particles, whereas surgical masks protected against an average of 78.2% of fine particles."

An October report in "The Conversation" noted that: "A study of one-layer tea-towel masks and a study of two-layer masks made of T-shirt material both showed at least 50 per cent protection for fine particles. Two cloth masks of unknown materials randomly purchased from street vendors performed just as well."

Remember, anything that cuts transmission, even if not 100% effective, helps us live with Covid in a safer way.

School's Out

The cases in schools paints a shocking picture. 

Once the isolation of direct contacts requirement was removed from any children not showing symptoms, the active new cases showed an R0 rate of 2 or higher. 

Week beginning 21 June: 29 students, 2 teachers

Week beginning 28 June: 53 students, 7 teachers

Week beginning 5 July: 107 students, 13 teachers

Week beginning 12 July: 224 students, 25 teachers

The biggest areas for transmission are secondary schools, where children move from class to class, unlike Primary Schools, where a class is for the most part, in one classroom. This is a key driver in numbers rising.

Government should be formulating a better strategy for return to school or it is likely the same scenario will play out in September.

Will we follow the UK in more vaccines for children at risk and also parents at risk?

From 19 July 2021, the JCVI [(Joint Committee on Vaccination and Immunisation) is advising that children at increased risk of serious COVID-19 disease are offered the Pfizer-BioNTech vaccine.

That includes children aged 12 to 15 with severe neurodisabilities, Down’s syndrome, immunosuppression and multiple or severe learning disabilities.

The JCVI also recommends that children and young people aged 12 to 17 who live with an immunosuppressed person should be offered the vaccine. This is to indirectly protect their immunosuppressed household contacts, who are at higher risk of serious disease from COVID-19 and may not generate a full immune response to vaccination.

Under existing advice, young people aged 16 to 17 with underlying health conditions which put them at higher risk of serious COVID-19 should have already been offered vaccination.

The JCVI is not currently advising routine vaccination of children outside of these groups, based on the current evidence.

A Curious Change in Ratios

"If you think you may be a direct contact but have not been told so by the Covid Safe team, you are not legally required to isolate. You are asked to consider your responsibility to the wider community and to avoid gatherings and public places where possible."

Are all direct contacts being picked up? And is the reduction  in PCR tests from three to one having a significant effect on the figures? Is the change from PCR workforce to lateral flow for some groups having an effect by not picking up cases?

Without data, it is hard to know, but something strange is happening. While the number of cases seems to be in decline, the ratio of symptomatic to asymptomatic has fallen from around 30%-35% (for most of the cases this year and last) to around 25% over the last two weeks.

Of course there are other factors at work here. 

The closure of schools, where R=2 - one individual transmitting Covid to two others, must be significant in the decline in the number of cases. This was an almost entirely vaccine-free environment - even most teachers had also not had 2 jabs. But this does not explain the ratio, as that was the same around 30%.

In the words of the song by Toyah, "It's a mystery"!