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The large fall in HIV diagnoses in London gay men is real and thanks to combination prevention, not just PrEP
Roger Pebody, 2017-04-06 16:00:00
The number of new HIV diagnoses in gay men attending five
key London clinics fell substantially during 2015 and 2016, Valerie Delpech of Public Health
England told the British HIV Association (BHIVA) conference in Liverpool yesterday.
Epidemiological analysis shows that the phenomenon is real. Diagnoses fell while testing rates dramatically increased,
showing that the explanation cannot be reduced testing. The CD4 cell counts of
newly diagnosed men increased, suggesting that fewer new diagnoses are indeed
the reflection of fewer new infections. The time from diagnosis to starting HIV
treatment has fallen.
Delpech said that the results were the result of combination
prevention – testing and 'treatment as
prevention'. Pre-exposure prophylaxis (PrEP) is likely to have contributed to the
fall, but to a lesser extent, she said. It could have more impact in the
Nneka Nwokolo of
the 56 Dean Street clinic agreed: “Although I think we all accept that PrEP
plays some part, actually the decrease started significantly before PrEP was
being used in any widespread way,” she said. The clinic quickly identifies and
engages the men with the very highest risk of acquiring HIV and encourages them
to attend each month for sexual health check-ups. GeneXpert testing for
sexually transmitted infections has reduced the time from test to treatment
from ten to two days.
importantly, a quarter of newly diagnosed individuals now start HIV treatment
within three days of diagnosis.
said that Public Health England had reliable data on new HIV diagnoses across
England up to and including the third quarter of 2016 (July to September),
whereas reports for the last quarter were still coming in. Nationally, there
was a clear fall in diagnoses in gay men between October 2014 and September
2016, but not in other population groups.
Moreover, there are
five clinics at which the falls in gay male diagnoses were concentrated. They
are all in London: 56 Dean Street (which accounts for over a third of
diagnoses), the Mortimer Market Centre, Burrell Street, Homerton Sexual Health
and St Mary’s.
Trends in clinics
elsewhere in London, and elsewhere in England, are different.
During 2015, there
were over 200 new diagnoses per quarter at these ‘steep fall’ clinics. In 2016,
this lowered to between 100 and 150 diagnoses per quarter.
This has occurred
against a backdrop of many more HIV tests being done and men getting tested
more frequently. Among repeat testers (men who had tested at the same clinic
within the previous two years), the number of tests done per quarter at the
five clinics increased from around 4500 in 2013 to almost 10,000 in 2016. The
greatest falls in diagnoses occurred in repeat testers, rather than men testing
for the first time at that clinic.
Delpech said that
clinics appeared to have got better at identifying men at greater risk of HIV
(for example, those with rectal STIs and those seeking post-exposure prophylaxis [PEP]) and encouraging
them to come back more often for testing. The number of men taking two, three
or four tests within two years has increased dramatically. Nonetheless, around half of
clinic attendees still test only once in two years.
The time from
diagnosis to starting HIV treatment has been falling for several years. This
has been observed across the country, but has been especially marked in recent
years in the five steep fall clinics. In 2011 the median was around 450 days;
in 2013, around 180 days; and in 2015, around 100 days.
As a result of both
faster diagnosis and faster treatment, the estimated number of gay men with a viral
load over 200 copies/ml at these clinics has fallen dramatically. There were
around 4000 men in 2014, falling to around 1700 in 2016. These numbers include the estimated number of men with undiagnosed HIV infection attending these clinics, together with men not on treatment and men on treatment but virally unsuppressed.
data on the ‘transmissibility ratio’, a new measure which could serve as a
proxy for the risk of onward HIV transmission in a clinic population and the
sexual networks they connect with. It is calculated by dividing the estimated
number of men with a detectable viral load by the number of men considered
‘high risk’, those with an STI in the previous year.
At the steep fall
clinics, there were 1752 men with detectable HIV and 3596 men at high risk,
producing a ratio of 0.5. (With a ratio below 1, the chance of transmission is
low.) However, at other London clinics, there were 1444 men with detectable HIV
and 868 at high risk, producing a ratio of 1.7 (suggestive of a greater
transmission risk). Similarly, outside London, the ratio was 1.7.
Other clinics have
seen increases in testing rates and decreases in time to starting treatment,
but the changes do not appear so far to be of a sufficient scale, or
combined in the same way, so as to result in the large falls in new diagnoses
observed at the five London clinics.
“We are witnessing and
recording an ecological experiment of the impact of combination prevention on
HIV incidence,” Delpech said. While the downturn in new diagnoses has only been
seen in gay men, she said that there was no reason why testing and early antiretroviral therapy (ART)
could not be scaled up in all people who are at risk of HIV in this country,
regardless of gender, ethnicity or sexuality.