Divers should consider waiting at least seven days after each dose of coronavirus vaccine before engaging in scuba or freediving activities, suggests DAN Europe.
The medical and research body has issued updated recommendations for divers who have already been vaccinated and might have suffered the sort of side-effects commonly associated with vaccines generally, such as headache, mild fever, nausea, pain at the injection site, dizziness, gastro-intestinal disorders or swollen lymph nodes.
The vast majority of side-effects experienced to date have been mild, says DAN, occurring mostly within 12-48 hours of the injection but occasionally up to seven days, and more frequently reported after the second dose. However, it says that these symptoms might be “further enhanced by diving conditions, such as immersion, pressure and hypoxic/hyperoxic environment”.
It also says that anecdotal cases of symptoms in divers make it possible that some of these effects could “temporarily influence the risk of diving-related illness” – though it insists that being vaccinated in line with the national roll-out plan is highly recommended.
The suggested seven-day precautionary interval should be extended to 14 days for divers who experience side-effects for more than 48 hours, or those with personal health-risk factors such as being overweight; having chronic metabolic disease (including diabetes); a smoker; or taking medication such as oral contraceptives that might increase risk of embolisms.
The 14-day recommendation also applies to divers planning to exceed no-decompression recreational diving limits.
Divers are advised to consult their GP if vaccination side-effects persist for more than 48 hours. If they do carry out what seem to be low-risk dives during the seven days after a vaccination and experience symptoms that could be related to diving disease, they should call a diving-medicine specialist.
Last May DAN published widely endorsed recommendations for divers returning to diving after a Covid-19 infection. With the current resumption of diving it has now updated and republished this advice to embrace additional knowledge of the coronavirus.
Divers who test positive but remain completely asymptomatic should wait at least 30 days from their first negative test before applying for fit-to-dive clearance and eventually resuming diving, says DAN.
Those who suffer symptomatic Covid should wait the 30 days and then another 30 days symptom-free before applying to a diving medicine specialist for clearance to dive.
Divers hospitalised with or because of pulmonary symptoms related to Covid are advised to wait at least three months before applying. They need to undertake complete pulmonary-function testing, an exercise test with peripheral oxygen saturation measurement and a high-resolution CT lung scan.
This three-month period also applies to any diver hospitalised with or because of Covid-related cardiac problems, after which a cardiac evaluation including echocardiography and an exercise test are required.
DAN Europe says that members can consult specialists from its diving support network as part of their membership benefits. Consultations may be needed to assess additional potential risks for divers who have had Covid in the event of lung barotrauma, lung bubble shunting, cardiac or other problems that might be experienced while diving.
The organisation points out that little is yet known about possible increased sensitivity of pulmonary tissue to the toxic effects of oxygen, so for technical divers extended breathing of hyperoxic gas, as in rebreather diving, should be avoided. Nitrox diving is not thought likely to be problematic.
Even less is known about the possible alteration of the bubble-filter function of the lung after a Covid pulmonary infection, says DAN, which recommends that to reduce DCI risk divers should keep well within no-decompression limits.