Waning immunity alert as fully vaccinated health staff get Covid-19

Seven of every 10 fully vaccinated healthcare workers in Western Kenya were infected with the coronavirus in the fifth wave, as Kenya fights rising cases dominated by the Omicron variant, a study has shown.

The study was conducted by the Lake Region Economic Bloc (LREB) in partnership with the PharmAccess Foundation at 55 participating healthcare centres.

It revealed that among fully vaccinated people, more health workers (72 percent) tested positive for the virus compared with traders (22 per cent), farmers (21.9 per cent) and learners (11 per cent).

This means that double-vaccinated healthcare workers are more susceptible to Covid-19 infection than the rest of the population.

The study, conducted between November 24 and December 26, sampled 7,280 Covid-19 tests, of which 7,197 had known outcomes.

Of this, 1,854 (25.8 per cent) tested positive for Covid-19. Although most confirmed positive cases were in unvaccinated patients (1,008; 54 per cent), a remarkably high percentage was found among patients with two doses (674;36 per cent) followed by the partially vaccinated (150).

Moreover, 16 (0.9 per cent) breakthrough infections were registered in people who had received a booster shot. An additional six patients (0.3 per cent) had unknown vaccination status.

“This situation is exacerbated by the fact that health workers were amongst the first to receive Covid-19 vaccines and therefore might experience waning vaccine-induced immunity, as has been reported elsewhere,” said Dr Shem Otoi, who makes Covid-19 predictions for LREB.

Preliminary sequencing work, he said, demonstrated a rapid transition in Western Kenya from Delta to Omicron from December 10 onwards.

Most frontline workers were the first to be vaccinated in Kenya in March 2020. With the vaccine waning, they are at risk of getting infected more than other populations.

The study also revealed that of 10 fully vaccinated healthcare workers, only one had a comorbidity.

The majority, 218, were in the 19-40 age group (75 per cent), 68 were 40-60 years old (23 per cent), and five were older than 60 (two per cent)

The most common symptoms were coughing (69 per cent), sore throat (57 per cent), fever (51 per cent) and headache (47 per cent).

The interim analysis demonstrates a disproportionately high rate of breakthrough Covid-19 infections in double-vaccinated Western Kenyan health workers including doctors, nurses, clinical officers, nutritionists.

The high number of cases in healthcare workers, Dr Otoi said, can be explained by their close contact with Covid-19 patients during the fifth wave, presumably dominated by the highly contagious Omicron variant.

With technical support from PharmAccess, LREB recently established a digital Covid-19 epidemic preparedness and monitoring system, Covid-Dx1.

The system digitalises important patient information including socio-demographics, vaccination status, clinical symptoms, comorbidities, occupation, geographical location, and reason for testing.

At the core of the system is a digitalised Covid-19 test result obtained centrally from the Kenya Medical Research Institute in Kisumu by PCR.

Based on the study findings, the researchers recommended that policies be adopted to prioritise frontline workers in administering Covid-19 vaccine boosters, preferably shortly after six months from the previous last dose.

“We support the position of the Ministry of Health on vaccine boosters though in the current fifth wave health workers should be immediately prioritised for vaccine boosters, at least in LREB, Kenya,” the study says.

Under new government guidelines, fully vaccinated Kenyans will get a booster shot six months after completing their primary series.

This will apply to any vaccine brand available in the country.

The decision followed advice from the Kenya National Immunisation Technical Advisory Group.

“Everyone who has been fully vaccinated should be in a position to get any vaccine of their choice for a third dose,” said Dr Patrick Amoth, the Health director-general.

There are enough vaccines for people who need a booster shot, said Dr Willis Akhwale, Covid-19 task force chair.

Officials wanted to start with booster shots for healthcare workers but after reassessing the situation, they realised they had enough doses for people who would need them, he said.

About 20,000 doses of booster shots have already been administered.

Kenya is expecting more than five million doses in mid-January.